blocking up underfloor ventilation

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blocking up underfloor ventilation

Postby justinandrowena » Sat May 26, 2012 5:15 pm

I read in a book recently to warm your house in winter that it is recomended to block up 1 side of your house's underfloor ventilation. Only I can't remember which side it was! I live in Perth, I am freezing, I have wooden floors on most of the house and a few rooms have concrete floors (AKA 1970's house with additions).
I have blocked up the holes around the kitchen pipes and now have left over spray foam!! (my daughter didn't want it- she prefered cake)
Thanks to anyone who can help,
Rowena.
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Re: blocking up underfloor ventilation

Postby hsvz » Sat May 26, 2012 7:39 pm

Not sure why you would block the vents. They are there to keep the moisture levels low. If the house is freezing there are other issues - Roof insulation, wall insulation, heating...blah blah blah.

Not much said about how you heat the house, gas, wood, reverse cycle ac and at the worst is electric heating ???

My background is 35 years in commercial air conditioning :D

Bit more info would be good :D
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Re: blocking up underfloor ventilation

Postby justinandrowena » Sat May 26, 2012 9:48 pm

My house is as well insulated as it can be without too much expense. E.g wall insulation and is north facing etc. I am doing all the right stuff to keep the heat in and the cold out, but i did read that underfloor vents were a bit of a throwback to our English herritage and being in Perth, rising damp etc isn't something we need to be to scared of. The book did only suggest blocking up one side only, but can't remember which side.
Rowena.
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Re: blocking up underfloor ventilation

Postby Cherokee Solar » Mon May 28, 2012 6:30 pm

Hi,

Yes. Don't block up the underfloor vents as they will build up moisture levels under the floor of your house. This will rot out the timber bearers and joists and also wet timber is an invitation for termites. :(

If you are in a bushfire area, your vents can be made of either: heavy duty aluminium, stainless steel or bronze mesh sealed to a fire rated wall such as (13mm fire rated + wet area plaster covered over with 6mm fibro cement).

Have you thought about packing insulation - for example fibre glass R3.5 batts - under the floor of your house? I've done that here and the timber floors are toasty warm (or at least not cold) and it gets cold up in the mountains north of Melbourne!

Nothing you can do about concrete floors. They are always hot in summer and cold in winter because they settle at the average ground temperature which in Perth can vary quite a bit.

Given the age of your house (1970's), it would be a safe bet that you have no insulation in the walls? I could be wrong, but at that time no insulation was put in. It has been only recently that building surveyors requested and checked this as part of a house construction requirement.

You can check for insulation in the walls by removing a light switch or power point (be very careful with this and remember to switch off the power) and have a look up into the wall cavity.

If you have weatherboards, it is a lot of work, but pretty cheap to do, but will take a lot of time, pulling the weatherboards off and packing insulation into the walls. They now sell R2.0 fibre glass batts for 90mm wall cavities and they are worth their weight in gold. Whilst you are at this put in a moisture barrier lining too as there may not be one. Plus with the exposed wall, it would be an opportune time to rewire and replumb the house.

If you have a little bit more money to blow: remove the internal plaster on the external walls and build another timber wall adjacent to the current external timber wall - so that you would then have a double stud external walls (make sure you match the timber studs). Into this you could pack R3.5 batts. This is the design I have here and it never gets below 12 degrees inside (without heating) over winter despite being sometimes less than zero outside. Over summer it never gets above 26 degrees inside despite being over 40 degrees outside.

You could also add a second layer of insulation in the roof. If you have a tiled roof, it is virtually open to the outside world and back in the 1970's they didn't install moisture barriers between the tiles and timber either.

Good luck! :)

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Re: blocking up underfloor ventilation

Postby Gordon-Loomberah » Mon May 28, 2012 6:50 pm

Cherokee Solar wrote:Have you thought about packing insulation - for example fibre glass R3.5 batts - under the floor of your house?


I haven't insulated under my floor yet, but definitely wont be putting glass fibre batts everywhere under there, as it would make it far too comfy for the bush rats! We hear them running around on the metal joists and bearers at night, but with some cushy insulation they'd never leave to go back into the scrub :!:

I may do some areas of it if I can satisfactorily enclose it to be rat-proof, but I'm thinking of stapling some aircell insulation under there, I think its only R1.3 or so, but it wont make comfy rat accommodation.
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Re: blocking up underfloor ventilation

Postby justinandrowena » Tue May 29, 2012 3:49 pm

Hi,
Thanks for all your ideas. Can't really do a lot about underfloor and wall insulation due to lack of underfloor space and lack of money. I'll just have to get out my thermals and get outside into the garden when the sun is shining!
Ta,
Rowena.
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Re: blocking up underfloor ventilation

Postby zzsstt » Tue May 29, 2012 5:19 pm

Gordon-Loomberah wrote:.... I'm thinking of stapling some aircell insulation under there, I think its only R1.3 or so, but it wont make comfy rat accommodation.


I've never been entirely convinced about AirCell. We used it under our house (unfortunately the builder stuffed up and attached it to the bottom of the joists, not the top, so the air gap is rather large), and I used it under the tin in the roof of my garage/playroom. Something makes me think it does better in the "under tin" application where it is reflecting a large amount of energy, than in the under floor installation. And it has the major issue that if it gets dusty it stops working because it is a reflective system. Dust gets everywhere in this country!!

If I was going to do the underside of the house again (and at some stage I might) I'd use a solid foam product. I used Isoboard extruded polystyrene under the Aircell (see, I told you I wasn't convinced about it!) in the garage. It isn't exactly cheap, but it's easy to work with - cut'n'snap or saw, and attach with screws with large plastic washers, and/or glue. It's R value is nearly twice that of glass fibre batts, and you try securing a batt to the underside of a floor! And, of course, it's not comfy for rats!
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Re: blocking up underfloor ventilation

Postby munrre » Wed May 30, 2012 11:07 am

I did a bit of research into underfloor insulation and for temperate areas (Adelaide, Perth?) there is not a lot to gain.

We also have wooden floorboards and ended up getting rugs, runners etc. Better gains to be made by ensuring all glass is well insulated. Heavy drapes, roller shutters, clear comfort double glazing etc.

I have a project going at the moment venting a fridge space from underfloor and early indications are that the temperature below the house is pretty stable at around 15 degrees.

If you have gaps in your floorboards or at the walls allowing cold air to blow in that is a whole different story.
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Re: blocking up underfloor ventilation

Postby zzsstt » Wed May 30, 2012 3:17 pm

munrre wrote:If you have gaps in your floorboards or at the walls allowing cold air to blow in that is a whole different story.


It also depends on the design of house. I would guess from the original question that the poster has "walls that reach the ground", and floors that are reasonably close to the ground such that the only air movement is via the breather bricks or vents. In that situation then even leaky old floorboards wouldn't be too bad (comparatively) because cold air is dense and will stay on the ground, and the air is not moving very much. But if the house has a large crawl space underneath, or has open sides (like a Queenslander), or any other design where the air can move freely, the problems will be much worse and insulation becomes absolutely required.
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Re: blocking up underfloor ventilation

Postby lad » Thu Jul 12, 2012 5:21 pm

UTas have been studying the effects of building type on heating/cooling

Construction
http://oak.arch.utas.edu.au/testcells/v ... icleID=470

Monitoring
http://oak.arch.utas.edu.au/testcells/v ... icleID=472

From this link, select download project note 3
the PDF contains more data and graphical comparison of the cells performance. The concrete slab floor anchors the building performance more closely to ground temp, where the others swing "wildly" with outside temp

After seeing this I have a concrete slab, on ground. Performs well Winter/Summer -2 to 40degrees
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