solar heating/cooling or ventilation for a new home? « Alternative Technology Assn Forums

Alternative Technology Assn Forums » Sustainable Building

solar heating/cooling or ventilation for a new home?

(30 posts) (16 voices)

Started 12 years ago by living sustainably
Latest reply from susambas

Tags:

living sustainably
Member

Hello everyone,

we have just bought a new house -- the developer made a big fuss of it being soo 'sustainable' -- well, it's nice that they claim that, but it's just according to the current minimum required 5 star energy rating (or so I hope).

It's a two-storey house, lower storey brick veneer, upper storey weatherboard, no south facing windows, all major windows face north and west.

We are thinking about getting an air conditioning unit, but also some solar or passive heating/cooling solution to help with both the heating and the cooling.

The loungeroom, though facing north, is overshadowed by the house next door and therefore quite cool in winter, and could need a bit of a boost with a solar heating system. The top floor will desperately need cooling, and possibly any passive and extra help that it can get -- it can even get quite hot and stuffy now, in winter. Two of the bedrooms have windows facing north. We will put shading (roller shutters, thermal curtains) over the window, but this will likely not be enough.

We have looked at HRV (http://www.hrv.com.au/) who take hot or (when the sun is down) cooler air from the roof space and pump it into the living area, then also there is SolaMate (http://www.sola-mate.com/) which uses a collector panel to heat up air, much like SolarVenti (http://www.solarventi.com.au/) does, only that Solarventi is integrating a PV panel at the same time which powers the fan, which makes it my current favourite. -- Also, SolarVenti addresses cooling, not just heating issues, like here (http://www.solarventi.com.au/generelt/koling.htm) where they draw cooler air from the cool side of the building, and then they even have earth (geothermal) cooling http://www.solarventi.com.au/generelt/koling.htm#jord which is just a gorgeous idea.
We are not the kind of people who set the air conditioner very low, in fact we would keep it off or at a relatively high setting most of the time. But then Melbourne has these blisteringly hot days when gets up to 42 degrees. And on those days, there tend to be more power failures. So a system that a) runs independently from the grid and b) uses 125 m of cool earth to draw the air through might be a godsend.

But then, I also heard of Venmar heat exchangers which would bring fresh air from the outside in, just heat it up or cool it down taking the warmth/coolness from the stale air from inside the building which is let outside.

And in addition, someone has recommended to just put a large fan at the highest in the house which will transport the rising hot air out to the roof in summer, and cooler air will rise from the bottom. The house is sitting on a concrete slab (which I think is a requirement for new houses), so there is no space with cool air underneath the house, as was with the house of the person who recommended that.

In addition -- creating cross air-flow by opening windows is something we'll likely want to minimse, the house is on a very busy road which can always be heard when the windows are open. It just turns out that in practice, when we open windows, we close them again as soon as we can. That means that we'd probably not rely on natural airflow, and actuallly need a kind of opening or fan that will bring fresh air in -- hopefully not wasting too much energy.

There are so many possibilities. We had a HRV sales guy over, but all he wanted was push his product, we'd rather like someone independent who could come and look at the house and recommend which kind of the different passive heating/cooling systems out there is best suited to our particular situation...

Or otherwise, how can we go about evaluating this ourselves?

For evaluating what the HRV could do, I would first need an indoor/outdoor thermometer, best with multiple 'outdoor' stations that I could put in different parts of the roof space. Where can I buy such thermometers? If we go for the 'top floor ventilation' solution, where can we get a fan with the required capacity, and how do I go about figuring out what capacity we require?

If we put the fan into the top of the staircase, then there is a likelihood that the bedrooms which actually need it don't get much relief. So where would such a fan be placed, or how does airflow get calculated?

(We already now have trouble heating the bedrooms at all, because the thermostat for the upper floor is located outside the bedrooms above the staircase and always gets heated by the rising hot air from the ground floor heating, and never thinks it's time to heat the upper floor now.)

But if we put a large fan into one of the bedrooms, would it then create an unacceptable draft in that room?

So many possibilities, we are totally overwhelmed, please, any help would be appreciated.

Thanks!

Barbara

Posted Thursday 20 May 2010 @ 2:18:26 pm from IP #
ghostgum
Member

I've looked at a number of these. I chose not to buy the HRV system (sales guy didn't listen to our requirements and kept pushing something that wouldn't work and wouldn't save us any money). I installed a solarventi to heat just the southern room that remained cold on sunny days. We also have ducted evaporative cooler.

The SolarVenti is good at heating on sunny days. On lightly overcast days when our PV solar system is putting out about 1/3 power, the SolarVenti doesn't run, even though I would expect there to be available heat. The SolarVenti also doesn't run on summer evenings when you want to exhaust the hot air from the house. I like our SolarVenti, but it is expensive for the amount of heat we gain.

Be aware that the HRV runs its fan a lot, and that the filter needs to be replaced every 1-2 years ($100 service call). If air from the roof space is closer to the set temperature than the inside, then the fan will run.

You can buy indoor/outdoor digital thermometers, with a 1-2m lead on the external thermometer. You could try putting this in the roof space, and extend the cable if needed. Measuring the roof space temperature would be a good idea before considering HRV. In my case the light coloured roof and the RFL underneath means that HRV won't work without a sola-mate.

I was trying to buy just the sola-mate alone without HRV, but that wasn't an option.

I suggest living in the house for 12 months first, monitoring temperatures, and thinking some more about what can be done and what you want to achieve.

In summer, an exhaust fan on the top storey drawing air in from southern windows on the ground floor is cheap to run, but never going to give you the same temperatures as a heat pump air-conditioner.

There are some interesting air conditioning ideas that aren't particularly cheap at the moment. An evaporative cooler coupled with a heat/energy recovery ventilator. An air conditioner with the condenser cooled by water. The ATA had melbourne branch meeting presentation on air conditioning recently and the presentation is on the ATA web site.

Posted Thursday 20 May 2010 @ 10:51:33 pm from IP #
Arne Hachmann
Member

Here is an article which you may find of interest: http://www.homedesigndirectory.com.au/articles/how-to-make-house-warmer-cooler.shtml
With regards to high tempeartures upstairs - you have the same problem as most people in new houses (most of them without eaves) - they get very hot upstairs.

Posted Friday 21 May 2010 @ 12:40:46 am from IP #
ghostgum
Member

Arne,

Some other comments on the SolarVenti that I bought from you July last year. I'm getting 20-25C temperature rise between the outside air temperature and the SolarVenti duct temperature using the SV14, inline with expectations. The SolarVenti is mounted at 90 degree tilt (vertical) above a window faxing north. You suggested using a 120mm electrical conduit as the duct to get higher airflow (because smooth walls has less air resistance). Air flow is good with a 4 metre straight plastic duct followed by about 0.7m of flexible aluminium to direct it down to the ceiling. However the rigid duct does result in the fan noise being carried through to the room, more noticeable at some fan speeds than others. I expect that a flexible duct would have been be quieter. I have placed R1.5 polyester batts over the conduit and aluminium duct to reduce heat loss from the room. When the house heater is running, my temperature logging shows that warm air moves from the room up into the duct, but the insulation appears to be keeping the duct warmer than the roof space temperature. Without the insulation I would have needed a butterfly valve to prevent air movement and associated heat loss.

Posted Friday 21 May 2010 @ 1:37:46 am from IP #
cool at home
Member

Think about adding some additional reflective insulation to the roof space eg: Air cell attached to the underside of the rafters. It could make a difference to the top floor, though I would always expect it to be hot-ish. Nature of 2 storey homes,and of course that is what makes the ground floor so good...

I would also recommend putting very substantial (but retractable) window awnings on your Western facing windows, and perhaps 'slatted' window shades (at top of window, horizonal) on NOrthern windows. Cotton canvas is very good (much better than the far more common 'acrylic canvas', though a bit less hard wearing). Roller blinds are too close to the window to be very effective. This will work to keep summer sun out while allowing what winter sun you can access into the house.

Thermal curtains are invaluable of course, with pelmets, for both summer and winter.

The key thing is to focus on your living comfort, not the temperatures per se. This will free you up to do a few things:

1. Think about the rooms that are most comfortable for the season, and where practicable 'live' in those, and then focus on heating/cooling only those. It is a waste of effort and energy to try to get your whole house to a great temperature. So don't put the kids playroom upstairs in summer, or your home office in the hottest/coldest part of the house.

2. Install lots of ceiling fans (nice big ones, run on low) which will have an enormous impact on how YOU feel while barely affecting the thermometer at all.

2. Let the bedrooms get hot during the day in summer (unless you have a shift worker in the house)- when you are occupying rooms downstairs, it really doesn't matter what is happening upstairs. 'Night purge' them thoroughly when the sun sets, with mechanical ventilation like an ecoPower vent (as window opening is not desirable for you).

4. In winter, heat yourself primarily and only when you go into rooms - small, directional heaters are best for this, although in family living spaces highly efficient RCAC can be good if you have little access to winter sun.

It's at least as much about the way you live in the house as the structure of the house.

Good luck!

Posted Friday 21 May 2010 @ 8:42:41 am from IP #
dymonite69
Member

I drive by a house each day to work that has used this concept to keep warm.

http://www.builditsolar.com/Projects/Sunspace/sunspaces.htm#Guides

Some look fairly cheap to build and they double as a greenhouse.

The key to passive cooling is firstly good radiant protection from the sun e.g. RFL, eaves, shade structures and high volume ventilation (e.g. 30-60 air changes per hour). You need to encourage cool air from the south side of the house and expel the hot air out the top. This may be achieved passively but sometimes a fan needs to help accelerate the process.

Posted Friday 21 May 2010 @ 8:59:54 am from IP #
living sustainably
Member

Thanks everyone for the suggestions!

cool at home: Awnings over the Western windows... would be nice, but will be forbidden by body corporate rules. (Over the Northern windows, they would probably be fine.) Also likely forbidden is to grow a deciduous tree or bushes in front of the Western windows; the house faces west (where the street is), and Australian natives are recommended, if not mandatory, for the front gardens; are there any deciduous Australian natives which give a useful load of shade in summer?

Ways of living: Of course. We don't have a lot of requirement for the bedrooms during the day -- but this may change as my daughter gets older and will want to retreat in her bedroom more often. And we don't normally heat (or intend to cool) them during the day. But then when it gets dark and cooler outside, we'd like to have a way to ventilate them quickly and effectively. No office in the house, downstairs is all open plan, which is also the kids' play area.

ghostgum, I can buy indoor/outdoor thermometers: Which kind, where? I went to Bunnings the other day, and depending on brand 50-90% of all thermometers on the shelf there there were clearly broken and didn't agree on the temperature. The standard digital product I see, e.g. at the Australian Geographich shop or at Jaycar electronics, is an indoor/outdoor weather station... we already had one of these before, and it went broken after a few month, insisting that outside it was constantly 70 degrees (Celsius!).

As for two-storey houses being naturally hot upstairs: I grew up in a two-storey house with a cellar and a third storey in the (lower, heavily insulated part of the) roof. The bedroom in the roof does not get terribly much warmer than the rest of the house, and there is virtually no temperature difference between the ground floor and first floor. The secret is that this house is reasonably airtight -- completely cast out of concrete which pretty much eliminates gaps where the floors meet the walls -- and double-glazing windows filled with argon and doors which close watertight, with double, thight-fitting seals (and an airlock at the front door). The house doesn't have fans at all to move air around (except a rangehood in the kitchen), and no, it doesn't have mould problems.

The article (http://www.homedesigndirectory.com.au/articles/how-to-make-house-warmer-cooler.shtml) is interesting, but I already knew most of it... that's the theory. In there, it is suggested that you could use a SolarVenti to warm the whole house, but I was told that it will in fact only do one room. And what about the ground cooling option -- has anyone here had that, how does it perform on >40-degree-days? How much area does it need?

ghostgum, the SolarVenti doesn't run when the sun doesn't shine? The brochure I got said there was also a battery option so it could also run at night. Maybe you could add a battery?

Our projected heating bill is only $400 per year, so any of these installations will never easily pay themselves off, they'd just add comfort and reduce CO2 emissions.

Thanks everyone!

Posted Saturday 22 May 2010 @ 1:25:13 am from IP #
Eco
Member

Two storey houses often have an overheating problem on the upper floor for two reasons: most heat that gets into the house (bottom or top floor) normally rises to the upper storey; and the upper storey often has little thermal mass to absorb this heat. (The ground floor slab is not going to extract any heat from the top storey air. Of course this is not a problem if the walls are concrete, as for living sustainably's earlier house, or solid brick or reverse brick veneer - plenty of mass available from the upper storey walls to absorb heat and stabilise temperatures.)

So stop heat getting into the house anywhere, seal leaks, good insulation, foil under roof, shading on windows. But the upper floor is still likely to get hotter than the lower floor (in a typical low mass upper storey house) so as Cool at Homes suggests, live downstairs on hot days and ventilate the 2nd storey hot air outside as soon as outside temperatures permit.

Posted Saturday 22 May 2010 @ 2:40:53 am from IP #
dymonite69
Member

I agree with Eco. A high mass house which is essentially half buried into the ground is going to have a much more stable temperature profile during summer e.g. Cooper Pedy. I don't think it would have much to do with the air tightness or double glazing - these things are more important in winter.

If you can't place external shading or vegetation over a window then a reflective tint (good, cheap) or roller shutters (excellent, expensive) are your next best option.

Posted Saturday 22 May 2010 @ 4:06:49 am from IP #
living sustainably
Member

Thanks all,

of course I'm considering shading -- have now also learned some about thermal curtains and know now that the first curtain I put is was done the wrong way!

To summarize, I need a curtain rail that bends around the edges, so the curtain can go right to the wall.

Warm air hopefully will stay behind the curtains - but it will rise, and if the curtain is not closed off at the top, it will escape there. One way to do this is pelmets, but here is an idea I got from a friend who is an interior architect: Let the curtains go from the ceiling to the floor, so the ceiling effectively seals them off at the top. This also makes the room visually higher. Of course the curtain should also be closed off at the bottom, so best reach the floor.

I'm seriously considering the "whole house fan" option and found this: http://www.pge.com/includes/docs/pdfs/shared/saveenergymoney/rebates/whftechsheetv5.pdf

One question here: Instead of having only one "whole house fan", what happens if there are 3 smaller ones, one in each bedroom, which add up the toe required capacity? Then every room would benefit from the cool air that gets drawn up by the fan. If there was only one fan at the top of the staircase, I am worried the cool air would be drawn up the staircase and right into the fan, not really getting into the bedrooms where it's needed.

Any ideas?

Posted Monday 24 May 2010 @ 7:14:04 am from IP #
dymonite69
Member

Info on whole of house fans by the US DOE.

http://apps1.eere.energy.gov/buildings/publications/pdfs/building_america/26291.pdf

You control the air flow path by choosing which doors and windows to open

Have you also considered an evap cooler. The move a similar amount of air.

Posted Monday 24 May 2010 @ 8:57:23 am from IP #
ghostgum
Member

For evaporative cooler, ask how much power it consumes with full fan speed, and lowest fan speed. Ours is about 800W full, 500W low. I would have hoped that on low it used a lot less.

Posted Monday 24 May 2010 @ 11:12:00 am from IP #
gully
Member

I can tell you they won't know I actually looked at the specs for spare parts for my evap cooler, before purchasing. Most motors are a 1hp (750 watt) motors or above (I think these are throttled from 75% to 125% to vary the fan speed). The water pump uses another 50 watts. This is for a Bonaire VSM-75. Breezair are supposed to be a true inverter-powered fan so may be more efficient, but from memory axial fans use less power.

Posted Monday 24 May 2010 @ 11:44:22 am from IP #
cool at home
Member

Re Whole of House fans... have had some experience with these, and be aware:

1. Can be incredibly noisey... and with mixed results (if result was brilliant you would put up with the fan noise, as you don't run it constantly... but I haven't seen brilliant myself, because of reasons in 2 and 3 below)

2. If you have multiple vents in the ceiling (multiple fan inlet points) the hot air you've just sucked in through one fan can be forced out the vent of another (back into the house), particularly if not all the fans operate at the same time. I have seen this happen even though it appeared there were adequate vents to the exterior in the roof space. I believe the system can only work well if you have a single fan sucking air into the roof space, with only vents to the exterior from there, and

3. You MUST have a cool air source to replace the air you vent. Perhaps a low window on the southern side of the house, with air-cooling shrubbery planted deeply outside it. Don't expect to just open a window on the western side of the house and presto, cooling breezes start flowing. The air will move of course while the fan is operating, but the fan is only intended to replace the air in the house and then be turned off. If you've sucked in a lot of hot air in, you may well make the house hotter than before you started.

I am sure these fans can work well in the right conditions, but having seen one implemented in the wrong conditions, they can be an expensive mistake too. Tread carefully!

Posted Monday 24 May 2010 @ 11:45:21 am from IP #
living sustainably
Member

We are waiting for our energy assessment report.
Nicholas_Thomas, while this sounds compelling...

The house is brand new... made to a 5 star energy rating... unfortunately, for that rating, "windows are windows", and so the windows are the cheapest kind you could have, single glazing, aluminium frames, and lots, and huge.

It could be that the best insulation would be to replace them with double glazing. But that could easily cost $30,000 or more. Very likely one could get a solar heating/cooling system for much less than that.

Ideal would be: double glazing and excellent thermal insulation -- so once heated, the house doesn't lose the heat quickly (in winter, at least, when you want it warmer than outside). Then also a solar heating system to heat the house up during the day, and being so well insulated, it would retain that warmth through much of the evening, when it's needed.

Then of course also decent shading and a cool-air ventilation system for summer.

Altogether easily way too expensive to be feasible...

Posted Wednesday 26 May 2010 @ 7:16:17 am from IP #
John
Member

Cool at home is correct about the noise of some whole house fans. My wifes family home in the USA had one that her dad installed in the mid 80's, I liked to call it the boeing it was that loud.From memory it was a combination of the fan noise and and the wind moving that made it loud.

The beginning of this year I was looking for an alternative cooling/ventilation solution for our place, with the cost of electricity going up I wanted it to be as energy efficient as possible.
I did a lot of research and in Febraury ended up going with a whole house fan from Air Exchange http://www.airexchange.com.au This is not like the fan I remember at my wifes family home, it moves a lot less air (1100cfm) and is relatively quiet (I would class it as background noise). Our house is approximately 220m2 and apart from the 3 or 4 unbearable days (when we used aircon) Sydney had this summer all we used to cool our home was the whole house fan. When we go too bed opening our bedroom window with the fan on creates a nice breeze, this may not be perfect as you as you say its noisy with the windows open where you live. This unit cost me $1000 back in Feb, I installed it myself apart from electrical.

Another product I only recently came across which could be good for summer and winter is from a company called Solect air http://www.solectair.com.au It looks like it can be incorporated into an evap cooler to heat your home in winter or it can be used on its own to provide heating during winter and a whole house fan in summer. The cost of the unit on their site is $1950 plus installation. I dont know what sort of air flow this unit will provide for cooling, couldnt find info on the site.

Posted Thursday 27 May 2010 @ 12:06:24 am from IP #
Buzzman
Member

ls
It sounds like you bought what you could afford: noisy, on a main road, in a complex; rather than what you would have preferred, and alas this too is true for most people.

I concur with dymo on the external roller shutters vs tint film. The former are dearer but work and work well, the latter is an el cheapo 'solution' that doesn't do all that much. But it is cheap. There used to be (and I'm sure if you ask) available hand-operated roller shutters that were a bit cheaper and easier to install than the electric roller shutters. They use a crank-handle that you move from window to window.....it might be a way of saving a few dollars.

Another issue you may like to spend some time contemplating is crafty, innovative ways to properly physically 'zone' the house into smaller areas. From what you said - all of downstairs is one large open plan area? This is not good, as you need to heat or cool all of it, even if you are using the dining area, but not the lounge, for example.

And being connected to upstairs via the stairwell, any attempt at heating downstairs and the stairwell acts like a chimney and draws the heat upstairs.

So figure out a way to block the bottom (or the top) of the stairwell off completely. Without seeing your plans I can't begin to advise how this might be done, but a very simple curtain rod with a nice curtain hanging across the archway at the bottom of the stairwell might be all that's needed.

I did this in a 3-storey terrace house I lived in years ago and cut the winter heating bill in half. No more heat escaping up the "chimney". Curtain doesn't need to be heavy duty, but a couple of layers of muslin (see thru) will do a lot, although obviously an insulated heavy curtain is better!

Use pedestal fans rather than ceiling fans. Good quality, 600mm minimum diameter 'industrial' style, 3 or 4 spd units that rev like a plane at top speed. You'll seldom use that except for purging, but the oscillating action actually makes you feel cooler in summer, and they cost only a cent or two to run, about the same as ceiling fans if not less. And they're portable.

The key thing is attitude. Changing your attitude to what is "required" as opposed to "what's more sustainable". For example: it's great to leave the small directional heater on when you are in a bedroom, but above 25 deg C it is wasted energy. So I advise my clients to use a large format digital thermometer, like the weather station, available most stores like K-mart, Dick Smith.

Then use this to "drive" the temperature and thus the energy consumption of your house.

"Set and forget" costs you money and is not great for the environment.

But "drive" the consumption yourself and it will fall.

Keep house temp between 20-25 deg C in winter; 25-29 deg C in summer. At 29 deg C you will be sweaty, but a portable oscillating fan and/or ceiling fan should provide enough airflow to 'evaporatively cool' you down.

The bottom line with heating is "heat the smallest area possible, for the least amount of time". So if you have the zoning done better, and watch the thermometer, when the temp gets up to 25 deg, turn the heater off. In a well insulated house it should only drop by 1-1.5 deg per hour, so should take around 3-4 hrs to get back down to 20 deg, when you either go to bed or turn the heater back on.

But utilising "minimisation techniques" is the only way to remain 'comfortable' and not use excess power. BTW, all the above imply using appropriate clothing, so warm trousers, long sleeves, jacket or jumper, even a beanie in winter BEFORE you turn on a heater.

For example, it is 19.5 deg C in my office as I type this and, dressed as above (cap not beanie) I am very comfortably warm.

Adjust suggestions according to your own personal internal thermometer. And enjoy the game!

Posted Thursday 27 May 2010 @ 7:14:33 am from IP #
living sustainably
Member

Thank you Buzzman,

if there were only an archway between the open plan living area and the staircase, it would be easy... we'd probably already have a curtain, and contemplate putting in an insulated door. No, the bottom of the staircase is completely open. The front entry door opens into a small entry area directly open to the living area and with no ceiling above at all, and only a 1.6 m high wall against the staircase. The staircase has no ceiling other than the ceiling of the 2nd storey. This arrangement is not possible to simply close off with a curtain.

But I also think that the "chimney" effect is not all that bad if the bedroom and bathroom doors (and windows, considering the gaps under the doors) above are closed, because then the chimney ends at the ceiling -- which is insulated -- and has one opening, which is the return air grille from the ducted central heating. Meaning the hot air rises, goes straight into the return air grille, hopefully needs less energy to be heated again, and gets blown downstairs again. It could be more effective (more warm air to go round; heats the upper part of the staircase, which is effectively the volume of another small room; has heat losses on the way), but it's maybe not all bad.

While downstairs is all open-plan, there is only a narrow pathway between the kitchen/meal area and the loungeroom, and we are contemplating closing that one off. The two already have quite different temperature behaviour. The north side of the kitchen is all glass doors which are currently single glazing and don't even close properly -- lose a lot of heat in the evening -- gain it on clear days when the sun shines in the morning. Then it's even too bright. I am scratching and scratching my head and trying to think of a way how we can keep the warmth of the sunshine in (and maybe distribute it on to the loungeroom) (in winter only), but the glare out.

I do "set and forget" the central heating because it's thermostat-controlled and programmable, so it doesn't heat at all during the day and the night, and not if the desired temperature is already reached. It's currently only working in the mornings when it's still dark and in the evenings when the sun is down, and I currently have it set at 19 degrees. Gas usage for heating is about 3-4 cubic metres a day.

When it heats the downstairs area, it will heat both loungeroom and kitchen, and that's not zone-able -- says the guy who installed the heating -- so there we'll try to find ways to improve that manually.

This is the typical suboptimal block: West-facing, other two-storey houses immediately right and left (to the north and south), very narrow, the next house to the North is only 1.5 m away, there are no south-facing windows in the ground floor (they apparently would intrude on the southern neighbour's backyard privacy).

But not all blocks can be optimally oriented -- after all, the street runs north-south, the block is wedged between two streets. You can't only have East-West running streets in a municipality. Given these constraints, I am determined to make the house as sustainable as it can be _under these circumstances_. If we can't do that, we can't build sustainable cities.

Posted Friday 28 May 2010 @ 2:39:15 am from IP #
DHW
Member

Here is another option for compact heat exchangers for domestic heating:
http://www.brazetek.com/products

Posted Saturday 29 May 2010 @ 7:05:14 pm from IP #
living sustainably
Member

I'm all for heat exchangers but don't see how these ones can be applied in our house. In some houses, maybe they can. As far as I see, they only are water-to-water heat exchanges. So it would exchange the heat in ... what water? against the heat in ... what water? Wouldn't you need hydronic heating first? That would be the 'target water' that needs to be heated, and where would the 'source' of water come from that it would be 'permissible' to cool down instead?

Posted Sunday 30 May 2010 @ 1:51:54 am from IP #
Greg
Member

If you are looking at air quality in your home there are Heat Recovery ventilators that should be able to do this job economically (~140W) instead of a whole house fan. I received a quote the other day from air-change company. About $1100 for the unit and (contractor dependent) about $1500 for fitting. http://www.airchange.com.au

Posted Monday 31 May 2010 @ 4:10:07 am from IP #
living sustainably
Member

Wow, thanks Greg! Something like that was definitely missing in the list of things to consider...

Posted Monday 31 May 2010 @ 10:06:57 pm from IP #
StuartElliott
Member

Hi Ghostgum (and others),

Re your comment "I was trying to buy just the sola-mate alone without HRV, but that wasn't an option". Just to clarify, the solamate system can be purchased from solamate directly as a kit without the HRV system.
Regards
Stuart

Posted Tuesday 1 Jun 2010 @ 3:18:01 am from IP #
Anonymous
Unregistered

Exhaust fans in the kitchen and bathrooms are standard equipment in new homes. They provide spot ventilation to expel moisture and odors from limited areas. With spot ventilation, people sense an obvious problem and then manually flip a switch to solve the problem. Your article is helpful to keep cool house. Thanks

Posted Tuesday 1 Jun 2010 @ 4:02:31 am from IP #
Arne Hachmann
Member

Hi Ghostgum.

Yes, fan noise goes up with rigid ducting. You may consider to use a flexible acoustic duct for the last 1/2 meter or so.
We now have some new much better flexible ducting than what I have been able to find earlier, which works well. We also have in line fans, which improve airflow. so if you want to reduce the fan noise - give me a call or email me - I am sure we can help!
Arne

Posted Friday 4 Jun 2010 @ 1:37:03 am from IP #
Gruen
Member

Great stuff everyone. I've given up on the idea of solar hydronic as I can't justify why it costs 3 X the price in Aus as it does in Europe. Anyway, I no longer live in a damp climate which is what hydronic is really great at tackling. As it no longer seems to rain in southern Australia, my heating/cooling requirements for our weatherboard shack have changed. I grew up in the desert, and mostly without aircon and have no problem with soaring dry temperatures. However, the last few Melbourne summers have convinced me that it's time to cool the house a bit.

I stayed with my sister in Melbourne over last summer and she has the HRV installed in her brick 50s flat with enormous roof cavity (minus the summer heat flush component). While it was not a terrible summer, it was still great to get early morning puffs of cooler air over us as we slept. We did not find the fans noisy at all. The air throughout her place was fresh and our sinses LOVED it. It's really the first summer I've not sneezed from one end of the day to the other. We now think heat exchangers rock, at least for what is now considered tiny living spaces in Australia (80-120 sqm).

Re claims by some manufacturers that filters never have to be changed: hmmmm. The HEPA filters in my sister's HRV unit are the same standard used in labs she has worked in, she rates them as very effective and they do need to be replaced every 18 months or so. The job of a filter is to collect gumpf so I'd be wary of any claims that you would never have to have a service call, or at the very least climb about in the roof space and give em a rinse.

So, I'm almost almost ready to act. I'm going for a simple PV system to cover our current and any excess power use resulting from the cooling/heating system ($3k interest-free over 24 months). I was going to go with HRV (quote of around $3k) but will also check out the other recommendations mentioned by the good folks here (Air Exchange, brazetek and Solarventi).

Posted Wednesday 9 Jun 2010 @ 12:25:06 pm from IP #
petacat
Member

I can give you some direct information about the solamate/HRV. I have that installed in Canberra where it works very well in Winter and averagely ok in Summer. What I do is have the bedrooms and kitchen heated by the HRV/Solamate. I use no ceiling heat - just a single solamate panel. This does a good job of warming those rooms to remove the chill and therefore reducing the need to heat them. I have a small gas heater that provides the active heating when the sun is not shining. That heater is designated as suitable for heating a small room but it does 60% of the house easily enough.

What I did to deal with summer heat was to install an opening skylight. That lets the hot air out at night. I have a cathedral style ceiling and the Canberra nights are generally quite cool so it works well here. In Winter the extra sunshine is welcome during the day.

Since I made these changes my electricity bills (used to use reverse cycle heating and cooling airconditioning) has dropped between 20 and 30% in winter and just under 10% of summer. Gas bills for winter are about the same or a little less.

Fan noise from the HRV/Solamate is ok in the daytime and noisy at night when all is quiet. I had them adjust the nighttime fan speed to almost nothing and that is ok.

Posted Saturday 12 Jun 2010 @ 4:02:03 am from IP #
Buzzman
Member

When it heats the downstairs area, it will heat both loungeroom and kitchen, and that's not zone-able -- says the guy who installed the heating --

.....get a new guy to look at your heating!!!

But I suspect he's right - once installed it is difficult to make changes easily or cost effectively. The fatal flaw in our building codes - they are piss weak on energy efficiency.

With the single return duct in the upstairs corridor your house conforms to the "minimum standard" that most such installs do in this country.

As I understand it from my (very limited physics) the "energy effectiveness" of recirculating heating/cooling systems is largely determined by the VOLUME of air the system has to shift, and this is, at least in part, determined by the total volume of air in the house.

In other words, the SIZE of the motor, which determines it's 'hourly usage' (as they tend to run at a constant speed once 'on') is determined by the VOLUME of air needing to be pushed around.

Ergo, reducing the VOLUME means that you can reduce the SIZE of the mtor and thus reduce the 'total energy requirement'.

THIS NEVER HAPPENS!!!!!!!

WHY??? Because the industry can't be bothered 'selling' you on the energy saving benefits of having a "system" engineered this way.

They go for "the average person's expectations" (which is fair enough, given that an "average" family may live in the house after you do). "Average families" statisticaly use more energy than "efficient families" BTW.

SO, what are the KEY issues you MIGHT be able to address, and how to do so?

1. The single return duct is a killer. If it is possible to re-engineer the system so you have a return duct in both kitchen and lounge (as well as upstairs) then you have a chance to re-engineer other elements of the system to be more energy efficient

2. Because of the above, the motor is larger than needed to cycle air through ONLY the area of the house you need to heat or cool. If you can improve the return duct scenario, and isolate the kitchen from the dining room by 'closing off' the hallway, then you could get away with a smaller motor.
BUT, even without doing that, if the other aspects can be fixed, you WILL use less power as the motor fan will switch off much sooner as it has less VOLUME of air to circulate. The less often the motor has to cycle the air volume, the less energy it uses, the lower your bills will be.

3. If the stairwell can't be closed off at the bottom, what about at the top? If you can also isolate the return duct upstairs, then you will NEED a return duct downstairs. So no point blocking the stairwell if you can't fix the return duct issue.
But maybe moving the return duct opening in the ceiling so it is DIRECTLY over the stairwell, and closing off the stairwell outside this???? Again, without seeing the house or your plans I can't confirm if this is do-able, but it's worth looking into.

I explain the need for the above to my clients this way:
If the air-con in your car is set to "Recirculate" it works more effectively (keeps you cooler) than if you set the vent to "Outside".
It's logical - you are 'recycling' air that has already been cooled, so it cools more quickly and stays cooler, longer.

Apply the same logic to your home. If you want to cool ONLY the kitchen area, where is the air being drawn from that is to be cooled? From the (much hotter) upstairs corridor!!
Logic tells you that the system can't possibly be working at maximum efficiency doing it this way, ergo, logic also tells you it must be using more energy than is desirable.

In a 'worst case' scenario, your heater guy will tell you it's not possible to re-engineer the system because the return duct would have to be installed in the ceiling space downstairs BEFORE the Gyprock ceiling is put in. Technically coirrect, but not an insurmountable problem.

You probably have a 'services' duct connecting upstirs and downstirs that it might be possible to run a duct through. Failing that, retrofitting a duct in a corner so that it penetrates the ceiling/upstairs floor/upstairs ceiling can be a way to connect back into the existing ducting in the upstairs roof space. Not cheap unless you can DIY, but NOT impossible.

Get a quote and look at what you would save by significantly improving your heating/cooling costs (use 30% as a minimum saving) and this will give you a rough 'payback' figure. From there work out if it's "worth" doing and decide whether you wouldn't rather do it anyway - for environmental reasons - and save up to do it.

NOTHING is "impossible" - just some things are more difficult and therefore more costly to achieve. Get at least two quotes and try to find a heating engineer who has some enviro-cred.

Hope that offers some ideas/opportunities.

Posted Sunday 13 Jun 2010 @ 7:54:24 am from IP #
living sustainably
Member

Buzzmann,

thanks a lot -- you have pointed out a lot of good points.

As for plans of the house, they are selling another one of this kind, at the time of my writing, the plans are online here:
http://www.mirvac.ca.com.au/photos/23028-Lot1137mp.JPG
What this doesn't tell you is that any walls that separate the staircase -- from the entry area, from the lounge area, from the upstairs hallway -- are only chest-high and don't go through to the ceiling, and where it upstairs says 'void', that means that there is no separating ceiling between the downstairs entry area and the 'void' upstairs area above it.

The staircase is very difficult to close off either upstairs or downstairs without any major structural changes, and the return air grille is in the upstairs hallway just in front of the master bedroom, so, not directly above the staircase.

Your point about the return air grille is well noted. Hot air rises. This currently (when heating) works in our favour, it draws warm air in and only has to heat that up a little more, hopefully. When cooling, it will work very much to our detriment. Maybe there is a way to get another return air duct from downstairs.

Anyway -- zoning needs to be reconsidered. Behind the walls and in the ceilings, there are all these ducts running through the house. There must be a way to close some off automatically according to our needs. We now have a alarm/home automation system which, fitted with its own temperature sensors in different parts of the house, could conceivably do the zoning job that the heating/cooling system as installed is failing to do. Please -- do you know if there are 'duct zoning' elements one can buy? I mean something that is inserted into a duct and can close it and open it at the flick of a switch. Such switching would then be done automatically by the atuomation system based on the temperature sensed in the appropriate (for this room only) sensor.

Thanks for all the input!

Posted Monday 14 Jun 2010 @ 11:56:26 pm from IP #
susambas
Member

Hi All
Has any one built a cavity heating and Cooling systen similar to a Solar Venti?
The above refers to a site http://www.builditsolar.com but I could not find anything on a home built DIY version to heat/cool a home using a roof cavity.
Can any one steer me in the right direction? plans etc to built it myself? Succes rate etc?

Posted Saturday 3 Jul 2010 @ 7:30:26 am from IP #

RSS feed for this topic