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Venting for top floor cooling???

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Started 12 years ago by cool at home
Latest reply from Chuck_Oz

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cool at home
Member

Our top floor gets hot despite having - 'on paper' - very good roof and wall insulation, windows, external canvas awnings, timber venetians and thermal curtains - all used very well 'granny style' (ie: closed on the sunny side then opened, thermometer to tell us when it is hotter inside than out so to open windows etc). But we don't have access to breezes due to our location and a problematic floor plan (although we were smart enough to put the bathrooms on the west, with 2 bedrooms facing north, one facing south).

We thought of venting the bedrooms directly outside, and put 1 closeable ceiling vent in each and 2 Supavents on the roof. This cut holes in the insulation (yes I know... everyone say 'doh' with me), so the vent covers are hot to touch and the top floor is still hot. Not a success at all, as far as we can tell.

We are now tossing up between:
1. Closing the ceiling vents and putting insulation back over the top, and top up the existing insulation from current R3.5 (batts plus sarking installed 7 years ago) to R4.5 (or higher) with Air Cell laid over the rafters
2. Extract air from the attic with a motorised vent (eg: 2 x Maestro), so that air is also drawn out of the top floor bedrooms - equivalent to 8 Whirlybirds, apparently. Could also top up the insulation...
3. Duct the ceiling vents directly to the outside with 'Vent a Room' kits or similar. Note that these 'whirly birds' are not powered, so I'm not at all confident they will get much air flowing. Of course, could still easily top up the insulation.

I believe far more in insulation than whirly birds (which I generally consider a supported employment program for aging tradespeople) but feel we lack good ventilation and need to solve this. Can't work out how to put windows in for cross breezes given the placement of internal walls.

Has anyone solved this problem? If so, how?

Has anyone out there had experience of the (mains powered) Maestro, with a view to how effectively it will draw air from the top floor and through the attic?

Any ideas I haven't thought of, but should?

Would really appreciate your comments.
Thanks
Susan

Posted Wednesday 3 Mar 2010 @ 12:40:22 pm from IP #
dymonite69
Member

I am surprised that with good shading, insulation and ventilation that you are still getting problems.

Has the foil sarking gotten dusty?

With regard to ventilation, are you actually able to get cool air to enter? Is it just being replaced by more hot air? The flow rates need to be fairly rigorous and best power assisted in your case.

Try opening windows facing away from the sun on the ground floor. The incoming breeze can also be cooled by directing it over a moist garden bed irrigated by drippers.

Posted Wednesday 3 Mar 2010 @ 12:58:18 pm from IP #
cool at home
Member

Thanks Dynomite - I have a window on the ground floor on the south side of the house, next to the water tank and over dense vegetation that has had an awning put over it and a security screen put on, so that it can be left open in summer as the coolest-possible air inlet. I would still shut this on a very hot day as the bottom floor will be significantly cooler than outside. But this window doesn't get breezes per se and I think the air needes to be dragged inside for it to be effective.

Posted Wednesday 3 Mar 2010 @ 9:16:56 pm from IP #
ghostgum
Member

Where is the major heat entry? Windows? Walls? Roof?
Would an IR thermometer plus knowing the R values help with that?

Given that it is two storey building could you arrange some form of thermal chimney to work during the evenings and overnight?

Posted Wednesday 3 Mar 2010 @ 10:19:04 pm from IP #
cool at home
Member

"Major heat entry"... I'm not quite sure.

House was built 7 years ago is for its time was very well spec'ed: R3.5 ceiling, R2.5 walls (both batts and sarking), internal walls insulated, solid core doors. It was a project home - though spec'ed far beyond that - and the builder wasn't very co-operative (or intelligent, perhaps) so I've always been a little bit suspicious about whether we got what we paid for. If I was building today I'd use Air Cell instead of sarking and really beef up the batts in the roof and on the western wall.

A number of downlights in the top floor (11) but most have isolite downlight guards now (can't physically get to all from the attic) and the insulation pulled back around the light.

Arcylic canvas window awnings are used well on all upstairs windows - down all summer, up all winter. French doors on SW side can let in heat during the day (try to keep these closed in the daytime, but sometimes forget), and do let heat out well at night - although cross breezes are lacking.

Windows are Comfortplus (over 6mm think, tinted, coated) - and again we've been a bit disappointed with that. Temperature of the glass seems to vary widely and we assume if glass is hot then heat is being transferred into the room. All windows have wooden venetians and thermal curtains (except for bathroom and french door, which each have wooden venetians and thermal curtains only respectively).

I presume heat is coming up the stair well from the bottom floor (which is pretty darn terrific - thermally speaking - it has to be said, so we don't want to change that), and that some heat is gettingin windows/walls/roof because it is not a perfect thermal 'box'.

On hot days in summer the bedrooms are too hot to be in. Has been fine up to now as we live (and play) downstairs, open up the top floor at night, and sleep under ceiling fans. But kids now need to study more and their rooms can be pretty awful.

Perhaps we should focus first on checking and improving the insulation, but now we've cut holes in the ceiling for vents and are not sure whether to invest in decent motorised extraction or to close them up again?????

Posted Thursday 4 Mar 2010 @ 12:03:50 am from IP #
dymonite69
Member

So before the house was lined, you actually saw insulation go in the top floor? Is it a standard BV construction? What area of wall is not shaded by blinds?

Posted Thursday 4 Mar 2010 @ 12:12:24 am from IP #
CunningPlansDept
Member

Good post, I've got the same issue in our 20yo 2 story with brick veneer upstairs and double rendered brick downstairs.
Too hot upstairs in summer, too cold downstairs in winter.
We put in woolcell ceiling insulation and magnetite windows which helps, but not enough.
Other trials have been sealing off the stairwell (fabric around the downstairs) to check effect of air movement between the two.

Currently I'm thinking about
1) running a vent from under the ground floor (which has moisture issues) and through a pipe in the ceiling to get some heat exchange before venting to a stack.
2) doing the double sarking with ridge cap vent that was in ReNew about 4(?) issues ago.
3) setting up a low power fan and ducting between top and bottom floor in the corner opposite the stairwell. It would be great in winter to send the warm air from the loungeroom down to the bedroom at the end of the evening.

I would love to put in an earth-tube too but our site is too terraced and developed to do that easily.

Posted Thursday 4 Mar 2010 @ 4:34:48 am from IP #
cool at home
Member

Dynomite69: "So before the house was lined, you actually saw insulation go in the top floor? Is it a standard BV construction? What area of wall is not shaded by blinds? "

No didn't see the insulation go in the walls, although we know have at least some in some of the walls. Did see the sarking go up - blue side facing outwards in accordance with manufacturers instructions so I believe that is OK.

Definately have insulation in the ceiling but in the area we can get to it was not laid properly and we fixed it, but we can't get to the whole attic as it is physically impossible to crawl through it all. We don't know if the product was the R2.5 we paid for, but I am getting the insulation checked next week.

Yes, house is brick veneer.

The western wall has relatively few windows (only bathroom windows) so most of it is unshaded (no awnings), but again walls should be R2.5 (with sarking). Our north facing bedroom with western wall gets quite hot despite having no windows on the western side, and we believe this is due to heating up of the wall. If I had my time again I'd really beef up the insulation on that wall...

Thanks for all your questions and comments - it is really helping me work this through.

Posted Thursday 4 Mar 2010 @ 12:50:30 pm from IP #
CunningPlansDept
Member

Hi Cool,
Another thought just occurred. If you can, check if the walls can vent between the footings and the ceiling. That can help a natural chimney effect as the wall heats up, but of course air has to get out of the roof too

And don't forget that the sun rises and sets ~30degrees South of the East-West line in mid summer (depending on your latitude).

Posted Friday 5 Mar 2010 @ 10:06:15 am from IP #
Chrisv
Member

Quote"(which I generally consider a supported employment program for aging tradespeople)"end quote.

Would love to help but I have to take a walk down to the wirlie factory with my walking frame and I do not wish to be late. Geez..............

cheers.

Chris

PS. Sell the house to some other bunny and move on.

Posted Saturday 6 Mar 2010 @ 11:43:18 am from IP #
cool at home
Member

Oh dear Chrisv... what can I say. I really don't think the things work... put some in against my better judgement and... well, they don't work!

CunningPlansDept... not sure what you mean by letting the walls vent between footings and ceiling, but I presume you mean can air flow upwards through the walls???? No, house is BV and they are lined (in the normal way) with plasterboard, with the gap being full of insulation.

Incidently, roof is light grey tiles.

Posted Sunday 7 Mar 2010 @ 8:46:21 am from IP #
CunningPlansDept
Member

Hi Cool,
I'd forgotten your insulation. I ask as my top floor is BV but there is enough of a gap between the stud inner wall and brick outer to allow air passage.

Chrisv,
Passing on the problem to someone who'll either just overcompensate with bigger air con or suffer without the will and resource to address the problem the way Cool is, is kind of antithesis to what I hope this forum is working towards.
Personally, even though I'm likely to be selling soon, I'm still pursuing the improvements that make my house more sustainable for it's remaining serviceable life.

Posted Sunday 7 Mar 2010 @ 10:45:12 am from IP #
cool at home
Member

Had the insulation checkede out yesterday - was installed by a project home builder when the house was built. Conclusion was:
- sarking is light weight (not the medium weight R1.0 we requested)
- batts are both lighter and not as deep as they should be, possibly only R1.5 to 2.0 (we paid for R2.5, didn't specify a brand as we then - 7 years ago - didn't know enough to do so).

I am now thinking of having Air-cell retro-fitted under the rafters (R2.8), and either replacing the batts with R3.5 polyester or just topping up with R2.0 polyester. Don't want to disturb the fibreglass batts if I can help it, but as those batts are light, I'm assumng poly on top will just squash them down and make them even more ineffective. Unfortunately the cost of removal is significant due to safe disposal requirements, and if I can cover them up it would be preferably.

So it seems this - along with poor cross ventilation upstairs - is the root of the problem. Ignormance on my part, and fraud and poor workmanship on the part of the builder. We will approach the builder to see what we can get, but they are in adminstration currently, so I don't hold out a lot of hope.

I am thinking now of closing the in-ceiling vents and putting vents in the eaves for the existing 2 whirly birds - I don't think they'll do much, but they should do a little. If I can get the insulation to a decent level then I think that will be sufficient. ????????????

Posted Wednesday 10 Mar 2010 @ 2:17:50 am from IP #
Benny
Member

I heard of someone who installed a second layer of insulation batts perpendicular to the ceiling joists and on top of them rather than between the joists. This would stop the second layer squashing the first layer. Must make it a bit tricky walking around in the roof space though (-;

Posted Wednesday 10 Mar 2010 @ 7:35:12 am from IP #
dymonite69
Member

Sorry to hear about the dodgy job. Bad business practices eventually catches up with a company. Unfortunately it is the clients that lose.

The heat reflective function of the foil is only dependent on the surface property. The thickness only affects the durability of the product.

Ventilating the room is more important than ventilating the roof space (assuming you can get cool air to be drawn in).

Nowadays there are heaps of composite batt/foil products made by different companies. You aren't restricted to Air-cell so you should shop around.

Posted Wednesday 10 Mar 2010 @ 11:15:44 am from IP #
cool at home
Member

Dynomite... do you think ducting each ceiling vent to a single whirlybird (non motorised) would do any good? I had planned to get motorised vents (Maestros) but am told these can't be ducted, other than the ecoPower, which are too expensive - and too big - to do one per room. Apparently they can't be ducted to multiple rooms either.

Thanks for the tip re the sarking (reflective foil)... that is very different to what I was told.

Susan

Posted Thursday 11 Mar 2010 @ 5:28:04 am from IP #
Daniel Boon
Member

I'm surprised nobody has asked for your location, for you to then ascertain what the orientation of your home is. If the house is hot upstairs with X insulation installed, is it possible adding more insulation will retain more heat if the insulation is already suspect (light weight) ?
Why use polyester (or fibreglass) ... why not cellulose ? It has less embodied energy and greater efficiency ...

I have provided my email to prompt me to respond as I don't visit the site regularly danielboonjp@gmail.com

Posted Thursday 11 Mar 2010 @ 5:55:50 am from IP #
dymonite69
Member

You need to know how much air the whirly going to move. If it is a passive one it is highly dependent on your wind patterns.

To give you an idea of what you will need, a whole house fan achieves between 30-60 ACH i.e. you will aim to shift a minimum of 30x the volume of air in the room every hour

Posted Thursday 11 Mar 2010 @ 10:18:33 am from IP #
gully
Member

What about a ridge vent? These sit right at the top (unlike whirleybirds which also need wind) and allow the roofspace to breathe whilst being weatherproof. No moving parts either.

Adding air-cell or similiar to the rafters will definitely help, as will ventilating the roof. Both of these are of more benefit in summer than winter.

For winter - I'd leave the R1.5 fibreglass batts in place. From what i've read it's a law of diminishing returns when it comes to R-values (eg. R1.5->R2.5 is maybe 10% better). A multi-pronged approach is best (eg. sarking + aircell + batts).

Posted Friday 12 Mar 2010 @ 4:35:48 am from IP #
John
Member

I was about to mention whole house fans but dynomite got there first.

I just installed a low volume one in my place and it has made a big difference, draws in outside air through windows and forces it out of the attic. I never had any sort of cooling/ventilation before this, apart from a pedestal fan that I would use on really hot days.

I thought about whirly birds but couldnt find any conclusive avidence on how much air would be extracted, apart from the solar star which says it moves as much air as 14 whirly birds.....

Posted Monday 15 Mar 2010 @ 11:36:34 pm from IP #
Daniel Boon
Member

I think 'cool at home' has left us talking amongst ourselves ...
Whirleybirds are detremental to a house in 'winter' months ...

Posted Tuesday 16 Mar 2010 @ 6:34:11 am from IP #
cool at home
Member

I'm here! I forgot my user name for a while, but I'm back now. Thank you for all your replies and heaps of useful information.

I am leaning towards additional reflective insulation attached under the rafters at this stage - quote for reflective (Air Cell R2.7)and additional batts (poly) was over $7K and we can't swing both right now.

I am still confused about what to do about the in-ceiling vents - duct to whirlybirds or just close over and replace the insulation. The vents close so other than the actual holes in the insulation I'm not worried about the whirlybirds being an issue in winter. Have the same worry about holes in the insulation in summer, but the trade-off might be OK if plain old whirlybirds ducted to ceiling vents would actually be useful.

Obviously there's more cost in ducting 5 ceiling vents each to a whirlybird and it would be easier to just close them up, replace insulation and see how things are post Air-cell installation.

Having just stuffed the whole thing up once, I'm touchy about how to proceed... but probably just need to bite the bullet and DO something.

Posted Tuesday 16 Mar 2010 @ 9:59:22 am from IP #
dymonite69
Member

Adequate ventilation still has to be part of the strategy. You can try stuffing as much insulation into the cavities and spaces but eventually the heat will transfer across (particularly on relentless summer heat waves) and will be trapped inside.

We have a well insulated and shaded house with minimal west and east windows. Yet even with a cool summer evening we need a good several hours of cross ventilation to drop the indoor temperature 5-6 degrees.

Posted Tuesday 16 Mar 2010 @ 10:16:48 am from IP #
gully
Member

Yep - agree with dymonite here. Our weatherboard heats up and cools quickly, except after a few days of summer heat as the batts are overwhelmed with heat. Whole-house evap cooling / good cross-ventilation and roof ventilation will help cool the house with airflow all through the night.

I wouldn't get whirlybirds and I certainly wouldn't duct to them.

Posted Wednesday 17 Mar 2010 @ 12:26:03 am from IP #
alfresco24
Member

Air stratification and the stairwell leading up will result in all lower floor area heat rising and accumulating in your second floor. If there is no door sealing off the stairs, either at the bottom or top then hot air will rise to the top space. Also conducted heat and leakage through floors and wall spaces upwards will contribute heat to upper spaces.
Try installing (lots of) controlable venting above the top of the stairs, and/or build a taller ceiling space above the stairs to allow hot air to rise above the top floor rooms and vent that.
Good luck.

Posted Wednesday 17 Mar 2010 @ 12:54:42 am from IP #
Johnnojack
Member

Alf said "Try installing (lots of) controlable venting above the top of the stairs, and/or build a taller ceiling space above the stairs to allow hot air to rise above the top floor rooms and vent that."

I agree. You have the vents in the top floor ceilings already but for them to be effective you need at least an equal size vent through the roof. Think large pagoda style ridge vent or similar. (the spinnys are never going to be big enough) Even then, unless you install insulated ducting to the roof vent from the ceiling vents you will only be able to use it after sunset when the roof space cools down. If you really need to use the upstairs rooms in the afternoon then a evap cooler pushing cool air in downstairs and hot air out into the ceiling may be the only option. Presuming you are in an area where evap cooling is an option.
FWIW I have semi 2 storey with 2nd door at top of stairs leading into roof space where I have 2400x400 roof vent. Sun goes down, open door at top of sauna like stairway, hot air rushes out. Love it.

Posted Wednesday 24 Mar 2010 @ 12:16:02 pm from IP #
cool at home
Member

Thanks for all of this folks. We are not naturally well served by breezes and have kind of stuffed up the cross ventilation upstairs a bit, so while we do have good doors etc to open up when the sun goes down, there's not a fantastic outflow of hot air by any means.

Alfresco, I think you've captured the problem really well.

Someone did once suggest a ducted EcoPower 400 directly above the stairs would be ideal, but that's a pretty expensive solution, so risky if it is wrong. But it sounds along the line of the recent posts.

Posted Thursday 25 Mar 2010 @ 6:05:20 am from IP #
Blueprints
Member

Given the extents that you have gone to without success, it appears to me that Johnnojack may well offering some good advice.

In my experience, without a continuous cooler volume of air being exchanged in the roof space, several times over every hour, heat will eventually radiate through your ceiling insulation no matter its R rating. Vents out of the ceiling space will assist of course, but the volume of air to be exchange is (most often) much greater that even the powered vents (38 cubic meters per hour) can draw from the roof cavity

The trick I have found is to actually pressurise the roof space and prevented heated air from entering or remaining in your roof cavity. An evaporative system is more than capable of delivering the high volumes (upwards of 100 l/s to around 2000 l/s) of fresh or cooled air required running from as little as 50 - 60 watts per hour on low speed. Much better than the powered venting system can achieve at a similar energy usage rate and noise levels.

I'd be happy to assist you design and size such a system, but yes, its not a cheap option. But, my 2 storey home stays at 26 degrees in the top floors even during a week long 42 degree + heatwave, with no significant change to our energy usage (we used to run a portable evaporative cooler in our downstairs family room before this). We could do more with window shading etc as well which will happen shortly to make this system even more effective for its running cost.

Posted Monday 29 Mar 2010 @ 12:43:39 am from IP #
gav3500
Member

If your location is dry enough you could fit an evaporative cooler. With the pump off they are effective at purging the air from the house. In Canberra with cool nights they are great for getting the cool outside air into the house.

Also with the windows direct beam (sun shining in) is only about 20% of the energy coming in through the windows I've read somewhere. The rest is indirect beam (general background brightness) and conduction.

You could also try temporarily blocking off access to downstairs. i.e. is down stairs cool because all its heat is pumped upstairs?

Posted Tuesday 17 Aug 2010 @ 5:50:14 am from IP #
cool at home
Member

Many thanks Gv3500. We're Sydney based, so I don't think evap cooling will do well for us, and yes... I think the downstairs is cool because heat rushes upstairs. As we spend most of our waking hours downstairs I consider that a good thing... until bed time (or if the kids have to study in their bedrooms).

Since I first posted we've installed Aircell reflective insulation to improve summer temperatures, and I think we now need to install ducted, motorised exhaust fan to the vent at the top of the stairwell... not cheap though! We are looking at an ecoPower, as the Maestro - which I like in a lot of ways - can't be ducted (according to Edmonds).

Posted Tuesday 17 Aug 2010 @ 7:31:28 am from IP #

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