I agree with norbert and dymonit69 in different ways...
Frames do matter. Quite a bit but still, you can compensate for almost anything if you try hard enough.
Double glazing, good frames, good window coverings and you can largely avoid having to heat and cool with some fuel. It is worth it in my opinion to be comfortable in extreme weather and to know that passive approaches consume almost nothing more for decades.
Frateco
Member
As long as you do the right things in protecting it, my opinion is that timber framed windows will be the best with respect to insulation properties. Wood is a great thermal insulation material.
But there are maintenance issues and if not given an oil-based protective paint system, the windows can distort and gaps can appear. But I will persevere rather than put PVC windows in. Don't care how maintenance-free they are, how good they look ... it's still PVC.
dubbo teacher
Member
Thanks Dymonite, Catopsilia and Co for very useful replies.
I have been unable to log in for a while. It's taken me some time (years) to get my head around some of this stuff. For example for a long time I couldn't really see where insulation and thermal mass were best placed - only that both were needed for desirable outcomes. Now I think I'm right to say that insulation needs to be on the outside - alround the house - and thermal mass on the north side floor and nearby internal walls but only if north side glazing exists to cater for it. And that thermal mass in rooms with no sun at all are actually counterproductive in that the cold thermal mass must pull warmth out of the air in winter therefore lowering the room temperature just when you want it warmer.
Thus my original concern about double glazing - it acts to better insulate year round but I was worried that it would slow the transmssion of warmth in winter time (with curtains open during sunny days).
I'm thinking now that on those nice sunny winter days following cold nights you could allow maximum warmth in by having the windows OPEN during the day before obviously closing them in the afternoon - as well as closing the blinds, curtains etc - to lock in the heat gains. It certainly seems as if DG is a sound investment (noting also the importance of frames, pelmets etc)
dubbo teacher
You say:
"thermal mass on the north side floor and nearby internal walls but only if north side glazing exists to cater for it. And that thermal mass in rooms with no sun at all are actually counterproductive in that the cold thermal mass must pull warmth out of the air in winter therefore lowering the room temperature just when you want it warmer."
Since we live in the same area, I have to say that I don't think that is quite right.
My experience here is in a thread on another forum:
http://forum.weatherzone.com.au/ubbthreads.php?ubb=showflat&Number=864613#Post864613
Later posts (and some earlier posts) with the same nom de plume also refer.
Posts #868562 and #869629 show that the outdoor subsoil temperatures are 14 degrees in winter and 26 degrees in summer, while the subsoil temperatures at the same depth under the house are 19 degrees in winter and 22 degrees in summer. Putting a well-insulated house on a patch of ground makes the sub-soil temperature perfectly comfortable in our climate. Therefore, your thermal mass will never get cold, even in the south part of the house. When being shown over a house with high thermal mass, people always put their hands on the bricks to see whether they are warm or cool. They are neither!
You need the right area of north-facing windows to maximise winter solar gain. Windows that are too big (especially tall ones giving a "waterfall effect" as warm air against the window panes is cooled more and more as it plunges to the floor) yield less nett heat gain than smaller ones.
Double-glazed windows let nearly as much sunshine through as single-glazed ones.
RE: open windows in winter
If you look at the items I linked in the previous post, dubbo teacher, you will see that it would seldom have been a good idea to open the windows on these winter days. The air outside was quite a lot colder than inside.
I can use a neat trick in my house, due to my choice of awning-type windows. When it is sunny and not too windy, the air touching the wall below the windows does get very warm. It convects upwards. By opening the window I can divert it into the room, giving both heat and ventilation.
Benny
Member
dubbo teacher/catopsilia. Re "thermal mass in rooms with no sun at all are actually counterproductive".
I've been thinking of starting a thread along these lines myself and to some extent agree with DT.
There's no argument that N facing glazing (preferably DG) and thermal mass that gets warmed by this free energy is a great advantage. But is the thermal mass in other areas of use ? If that thermal mass was cold then it would be counter productive but why would it be cold ? As Cat says - if it was well connected thermally to the ground then it should conduct heat from the ground and stay reasonably warm - but is it ? Perhaps a concrete ground slab directly on the earth would be but what about a brick wall. Then again why would the wall get cold ? Only by conducting its warmth to a colder medium - the air in the room if that gets cold or to the cold outside if its not well insulated. I was thinking that the criteria for using thermal mass in areas that do not get direct, free external energy would be whether additional heating is every used in those areas. If you don't use extra heating then the thermal mass will tend to smooth out temperature variations i.e keep it warmer at night but not let it get as warm during the day. The thermal mass won't make it any worse. BUT if you do use extra heating such as GAS, then the high thermal mass in the wall will mean you will need to use a lot more energy to get the room to an acceptable temp. I realise that energy won't be wasted as it will be absorbed by the wall and later released when you turn the heating off (as long as the wall itself doesn't leak energy). All that will happen will be that the time constants will be longer. The heating will be on for a long cycle before settling down and can maybe be turned off overnight. With no thermal mass the room temp would come up much more quickly, but also cool down again just as quick (depending on insulation) and may need to be left on overnight. The nett energy used would be very similar. I guess this is the experience of trying to heat up an old house with lots of thermal mass it is said to be cold because it takes so long to warm it up.
Anyway maybe I should start a new thread and wait for Dymonite to leap in (-; The ideal house - very lightweight double skin walls (no thermal mass and hence little embedded energy) with very high insulation + an active area with N facing double glazing and high thermal mass directly exposed to store the free energy.
dymonite69
Member
Heat is the energy. The sun (and a much lesser degree,the air) is the heat source. Mass is the battery. Insulation stops the battery from leaking.
Would you put a battery in your house and not connect it to your solar panels?
Same effect if your battery is not in a sunny room.
Would you not insulate your battery?
Same effect as not insulating your walls.
If the battery gets full, it gets hot. Is this a good thing in summer?
Same effect in a double brick house without shading.
Thermal mass is not free energy, it is a storage device. It can be either source or sink depending on conditions.
dubbo teacher
Member
I agree with Benny re ideal house and can also understand the points made about thermal mass evening out extremes but I certainly know that the concrete floor in the bathroom and laundary in my house that see no direct sun get awfully cold ...and they have plenty of thermal mass.
As Dymonite says thermal mass 'can be either source or sink depending on conditions'. So if you are aiming for a house with little or no artifical heating it's gotta be important to have as much mass as possible exposed to direct sun I would have thought.
I also understand that insulation will of course slow down heat loss but once heat is eventually lost - this time of year - how do you warm it up without artifical heating if there is no direct sunlight?
dymonite69
Member
If your battery is too big (overmassed) and you don't have enough free energy (sunshine), then you will need to charge it with your own money (home heater).
The right amount of mass is that is enough to store winter sunshine so that it can be released at night. Too much mass and you have to heat it yourself. Too little mass and there is none to release later. You will generally need less mass as night time temperature rise. You also need insulation or the mass will cool down too quickly.
You can use mass to keep a house cool but you have to be careful.
Firstly keep the inside of the house well shaded so that the no direct heating comes from solar radiation. Place the mass in a shaded area to store the excess heat contained in the air. At night allow cross ventilation to drain the battery before the next day.
If you don't this right the battery will just become another source of unwanted heat.
Jeffbloggs
Member
@benny, Dynomite, Dubbo Teacher
on the point of thermal mass is not free energy: all energy from the sun is free, but storing it effectively in a thermal mass will cost you something...
Besides the reason why we don't have free energy is because we can't afford to!
The "free" variable is a direct product of the economy, not of physics or science.
Thats my two cents anyway 
I think the best thermal mass to use to store heat is water; it's thermal capacity is about 4.18kJ/Kg/K, concrete is only 0.75 and air 1. But it is important to note that this is per kg, so per volume this equates to roughly 4180, 1350, and 1 respectively per cubic meter. As a rule of thumb water will store the equivalent of 1kWh (1.16kWh to be exact) of heat per 10c temperature difference and 100kg (or litres) of water. The same concrete mass will only store 0.2 kWh of heat respectively. So water is about 5x better than concrete at storing heat. Air is a factor 100 less than that again. In fact the 3% water vapor in air can hold an 8th of the heat the air itself does. Thats why human perceived temperature/heat comfort is actually related to the dew point of water, so if you want comfort and efficiency for climate control then humidity must be factored in. Plus water can increase its surface area to absorb or emit the heat via highly thermally conductive metal radiators. Solids can't accomplish this feat easily.
The other advantage with water is that you can utilize a hydronic system and decouple the thermal mass from the energy source ie permanent insulated tank for heat storage, solar hot water heating/shallow geo-thermal heat pump, and then use a simple circulation pump to distribute heat where and when required. You can't do this with a solid thermal storage system like concrete unless you get your house to rotate and follow the sun(which has been done before!) This also allows for flexibility with the actual house design to make the most of the location like views, road frontage, north facing solar hot water, PV etc. Using this type of system makes thermal mass storage an active system rather than a passive one, it can then follow actual demand rather than just produce a thermal buffer.
There is also the option of using the hydronic system for cooling as well, preferably using vertically mounted floor to ceiling convection radiators. These will create their own air flow for heating and cooling and no forced ventilation system (fan) is required. One thing that can be done is to cool the thermal mass during the evening in the summer months using off-peak power, and take advantage of the lower temperature at night using a solar radiator as part of the heat pump system.
If the hydronic temperatures fluctuate under 0c then i'd recommend using a coolant, that should get the system down to -30c without any issues.
These systems are quite common in Germany with come houses being able to maintain the temperature of a 4x2 house over the winter (down to -15c) for up to six months of the year using just a 1kW heat pump.
Of course they use double and even triple glazing in Germany...just to get back on subject... Aluminium windows have a thermal conductivity of about 180W/sqm C, glass is only 1.1. This means (without going into the air flow dynamics of convection of the glass vs frame) that on a 1sqm glass window with a 4cm frame will transfer 26X more heat through the frame than the glass. Aluminium is a metal heat conductor, one of the best in fact (thats why car radiators are made with ally), glass is a ceramic and they can be both good insulators and conductors of heat, in the case of glass its leaning more towards an insulator and is less of a conductor than concrete, soil and stone.
Double glazing only works with plastic (PVC etc) or timber frame. Timber is better than plastic by a factor of about 5-10 times, depending on the plastic used, but it also requires maintenance. Double glazing will not reduce energy consumption unless it is installed properly (PU Foam)and efforts are made to reduce all thermal bridging in the house, and that the house is significantly insulated. Leave the window open and see all of your efforts leave the building. Have a look at real heat recovery ventilation systems (not the bogus roof space ones) to increase inside air quality, preferably one with humidity control. They can achieve up to 90% eff. and aren't as expensive as one would think.
dubbo teacher
My temperature measurements on the surface of my floor slab ARE in the bathroom, and the floor does not get any direct sun. You can see on the graph in the link below that the minimum temperature on this floor did not get lower than 16 degrees in mid-winter when the outdoor maximum had been only nine degrees. I stand on that tiled floor in bare feet practically every day of the year.
http://forum.weatherzone.com.au/ubbthreads.php?ubb=showflat&Number=874144#Post874144
Why don't you come over and look at the set-up some time? I could easily put you up.
The forum that I posted the graph on has a system for passing messages to posters.
There is more about the house here:
http://www.cyberspeights.com/index.php/en/sustainable-living/housing/13-comfort-in-an-unheated-solar-passive-house
dymonite69
Member
I don't think the data necessarily supports the conclusion.
Isn't it inefficient to allow the thermal energy to be conducted through a high mass material to reach another room? A lot energy is required just to raise it to comfortable temperature.
You could make the sun-exposed area high mass to absorb the heat and keep the non-solar areas lightweight and highly insulated. Heating energy can then be transferred by convection with little energy taken up by the intervening mass structures.
dymonite69 says:
"Isn't it inefficient to allow the thermal energy to be conducted through a high mass material to reach another room?"
There is just one inefficiency involved here: the inefficiency of continuously heating (or cooling) the whole of a large house for the comfort of a very few people moving about in it from time to time.
I used to be horrified to see overseas visitors sitting in their rent-a-cars with the engine running to operate the air conditioner. Then I realized that the volume of air they were cooling was very small indeed (say 1%) compared to that being cooled in an air conditioned house to get precisely the same effect.
To get best results from thermal mass in a climate with temperatures ranging from far too cold to far too hot the mass must be large, say more than 100 tonnes. It goes without saying that this should include a concrete slab floor on ground. In such a volume of thermal mass (a "heat bank") temperatures change very little (less than 10 degrees) and they change very slowly, taking days, weeks, or months.
The temperature on the floor in one room will be much the same as that in another.You can't stop the heat moving around the slab even if you want to. Stopping the stored heat from getting in and out of the house is the main task.
The surfaces of the heat bank receiving sunshine should, as everyone knows, be hard dark material. Other surfaces of the heat bank can vary without changing the heat flows much. In south-side bedrooms, carpet on the floor does no harm at all.
nimm
Member
I don't have extensive data logging taking place like Catopsilia (yet) but I do have a thermometer in our place (table height) and check it every day multiple times per day.
FYI I live in a rammed earth house with polished concrete floors in most areas and battened down wood flooring in the rear (south facing) rooms. We're in the Perth hills where it tends to get a bit colder than Perth, unfortunately I don't have an outdoor thermometer so can't give location specific outdoor temps. However over the past couple months we've had some really cold weather, 15+ days of below 5c overnight temps (and usually close to zero) followed by some rain for a couple days and another spell of really cold nights.
Early winter the indoor temperature ranged from around 16-22C. For most of the winter the range has been 15-20C and for the coldest periods it's been 14-20C with a couple mornings at just below 14C. Note we have zero heating, just the sun.
The nice thing is this is the temp throughout the house. By no means is it "warm" but it's also not freezing. Basically you adjust the right level of clothing and then you're comfortable. Since the temp changes slowly and it's consistent through the house you don't feel like you're getting hot and then chilled etc...
In summer we're in the 20-28C range with some days topping 30C if we get some hot evenings. We also had a 3 day heatwave of daytime temps > 43C and very warm nights and that was the only time it exceeded 30C inside (I think it got to between 31 and 32C). We also have no cooling apart from ceiling fans.
I grew up in Sydney in a wooden house with no insulation and I remember having big difficulties sleeping sometimes in summer when it was crazy hot and a bit humid. Here however, the entire summer I never had issues sleeping because the indoor temp would always come down by then (peak temps would be midday into the afternoon but then drop as sun went down).
There's also plenty we can do to improve the summer performance because we're getting sun on the east wall for 2hrs between 10am-12 (sun gets over tree canopy) and then again on part of the west wall all afternoon. I plan to screen these in the future (vines/decidious trees/shade cloth etc...) which should make a reasonable diff.
dymonite69
Member
Heated air is a very low energy way of maintaining thermal comfort. If the house is well insulated and allows zoning then not much energy is required to bring up the air temperature and for it to be maintained.
However, air is a poor storage medium. Mass is better at this but it requires huge inputs to get it to comfortable temperature. The stability of the temperature occurs despite major in or outward fluxes of heating energy.
For heating purposes, it is uneconomical having more mass than is possible for it to be heated by the sun. For cooling purposes, it is redundant in having more mass than is possible for it be cooled by summer breezes.
Jeffbloggs
Member
@ dynomite
I agree with your statements in general, and would like to point out that this is exactly why water should be considered as a thermal mass storage medium as proposed in my post further up. With water it is possible to add/subtract temperature as required without having to overcome built in thermal masses like concrete, simply by changing the temperature of the water before it enters the radiator in the desired room. Plus adding some simple underground pipework (or shallow geo-thermal) can significantly add thermal mass if required. A fixed thermal mass will only act to buffer the temperature, a moveable one will allow real-time control of temperature.
dymonite69
Member
I have another idea about using water as a thermal mass medium. You can decouple the system and use it for both heating and cooling.
By turning the entire roof into a solar pool collector and having a hydronic slab, you can use it for collecting heat in winter or radiant cooling in summer. The function depends on what time you turn on the pump.
You may need a diverter during summer to dump excess heat elsewhere.
Jeffbloggs
Member
I agree with the decoupling. But it needs to go even further if you want real-time temperature control. For heat collection use a few, simple, of the shelf vacuum tube solar collectors on the roof (is this what you meant with "solar pool collector"?) with an insulated, preferably below ground water heat storage tank. Then use radiators as opposed to a concrete slab as it is better to have the temp control decoupled from the thermal mass of the slab. In Germany they always insulate the top of the slab, then apply hydronic heating coils and finish off with a self-leveling screed.
When i look at energy management in a house/room I always break it down as follows:
- Temperature control
- Ventilation and Humidity
- Windows/lighting/solar heat gain
These three items need to controlled individually from each other. For example:
In a winter day you want warmth, light (possibly thru a window), but with good ventilation without energy loss (so no open window rather a HRV).
At night you want warmth, but it will be nearly always be artificial (not solar), so from a heat pump or water thermal store. Plus you need to add artificial light, at which point the window becomes useless and counter productive, as you will loose your temperature through the window even with double glazing etc. The ventilation system can however continue to run via the HRV and provide fresh air to the dwelling.
In a summer day the opposite becomes true. A window will introduce unwanted heat if unshaded, and will still convect outside heat if shaded. But a window is good for natural light, but useless once again for efficient ventilation though (so stay with HRV). If air-con is used then window area is a liability.
At night you need to cool the house down, at which point in most regions, opening the windows for cross ventilation becomes important for certain periods of the year. If the temperature stays high at night and air-con is used then the windows remain a liability.
I think it is self evident that the variables in a house energy demand require a system that follow demand, ie active vs passive system, and such a system needs to utilize a movable thermal mass like water. Everything else will become a compromise between the seasons.
dymonite69
Member
JB.
I agree with this in concept but there is a cost for the added layer of complexity of control. ET is not ideal for radiant cooling. You need a large collector area for heat transfer, not high efficiency to obtain high temperatures. A Solar pool collector would be cheaper.
Jeffbloggs
Member
Dymonite
The reason behind using an ET or similar is to reduce the size and cost of the insulated thermal water storage tank, by increasing the temperature it is stored at, and therefore increase the thermal energy stored. This has follow on effects throughout the whole system in relation to plumbing/insulation/radiator requirements and circulation pump sizes. On the other hand a pool collector would be a reasonable radiant cooler, but a radiator similar to a vehicle radiator with forced ventilation (12v 30W fan) would be cheaper to install, maintain and actively control especially when used in conjunction with a water heat pump system. I think such a system would have to be optimized for the location and climate it is used in, and maybe a combination of collectors should be used, pending budget restraints and overall system effectiveness.
dymonite69
Member
No point in creating high density storage. The hotter your stored water, the faster it will cool - Newton's law of thermodynamics. The energy is wasted.
You only need a radiant temperature of 27 degrees Celcius for comfort conditions. Keeping the water at this level reduces losses. You only need higher temps for a HWS or steam generator. That's why ET are more useful for these greater extremes.
Jeffbloggs
Member
That statement is relative the amount of insulation you use around the tank and a high density storage is more cost effective in both storage and distribution of that heat.
The same rules apply with your 27c radiant temperature, this only works if you have enough (uninsulated!) radiator surface to transfer the energy into the air, over the specified time. Low energy density systems will always be bigger in every system component, but not necessarily more cost effective. Also it is possible to utilize the water thermal store for HWS, every HWS boiler does this.
BTW The laws of thermodynamics came from: 1st law Rudolf Clausius (1850), 2nd law W T Kelvin/Carnot/Planck (1870s), 3rd law Walter Nernst (1912)....this was a while after Newton died in 1727, besides, I thought he done that apple thing...;)
dymonite69
Member
I meant this:
http://en.wikipedia.org/wiki/Heat_transfer#Newton.27s_law_of_cooling
I would use the slab as the radiator. It is already there.
Jeffbloggs
Member
Dymoman
Okely, Newton law of cooling isn't a law of thermodynamics... But Newtons law of cooling would apply here as well. Not all houses have a slab and a slab is not that effective in a active thermal store system, only in a passive one. I'll stick with what they have been doing in Europe for 60+ years, with floor heating that is insulated from the slab or a metal radiator. The heat conductivity speed also further negates the daily abilities of a massive slab.
Norbert
I tried to get back to the subject of the thread a few times...but no one seemed to notice what my opinion was on different types of windows or frames...
dymonite69
Member
JB claimed:
"Double glazing only works with plastic (PVC etc) or timber frame."
"Double glazing will not reduce energy consumption unless it is installed properly (PU Foam)and efforts are made to reduce all thermal bridging in the house"
The effectiveness of DG is independent of other sources of thermal bridging. It is the air between the panes that insulates not the glass.
Other sources of heat loss through the building envelope also need to be addressed (including air infiltration) but this is a separate issue.
Even with a well sealed and insulated house, the windows (double glazed or not) still end up being a major source of heat loss.
Jeffbloggs
Member
Please read my comments in context, my next statement was: "Leave the window open and see all of your efforts leave the building". My point being that in order to control heat transfer, every effort must be made to insulate the whole house. Leave one "window" open and you loose all the benefits. Likewise install to many passive windows, even double paned ones, and it will not miraculously insulate you home.
On the subject of how double pane glass reduces heat transfer; I would like to point out that double pane glass only reduces convection of heat over the surface of the glass. Unless there is a coating (like a tint) it does not significantly reduce radiated heat and only doubles the resistance for conductivity through the physical doubling of the panes. An effective insulation is only achieved when all three forms of heat transfer are reduced, these are convection, conductivity and radiation.
http://en.wikipedia.org/wiki/Heat_transfer
Some handy stuff here on the web-site of the awa (Australian Window Association), which administers the wers Window Energy Ratings Scheme:
http://www.awa.org.au/members-only/Good-Energy-Efficiency
It is in the Members Only section so it is something you are not supposed to know.
My windows' ratings (1998) were issued by the Australasian Window Council, which seems to be still active. The politics relating AWA, WERS (which has its own membership list) and AWC, not to mention BCA, would seem to be complex.
dymonite69
Member
The relative contributions of radiant, convective and conductive heat transfer are not equal. Window coverings will alter this further.
Effectiveness is contextual to the climate. Single pane is entirely adequate for Darwin. Triple glazing might be better than double glazing but it becomes a law of diminishing returns. Cost-effectiveness should also be considered.
