attic Insulation

listermint

MicktheMan wrote: »

I didn't say AT on its own. I advised to initially concentrate on the probable air tightness weaknesses rather than insulation weaknesses to address the largest heatloss component.

If hes doing it he needs to look at it holistically. no point patching up airtight tape if the air behind the wall is same tempreture as the air outside the roof tiles.

Its not one or the other, its both.

MicktheMan

listermint wrote: »

If hes doing it he needs to look at it holistically. no point patching up airtight tape if the air behind the wall is same tempreture as the air outside the roof tiles.

Its not one or the other, its both.

Not necessarily. Depends where the thermal envelope is! Normally in room in roof situations, the thermal envelope follows up the knee walls making the crawl space behind the knee wall a cold space. By all means ensure the knee wall is insulated adequately, but this will have little impact unless and until the air tightness weaknesses are addressed.

Again, I never said its one or the other. I said to address the probable biggest issue first.

GreeBo

listermint wrote: »

If hes doing it he needs to look at it holistically. no point patching up airtight tape if the air behind the wall is same tempreture as the air outside the roof tiles.

There is though, reducing the number of times the air is exchanged in your house will have a massive impact on your heating.
Once the air stops changing/escaping its far easier to heat this air and maintain that heat in your house, even if that heat is still being lost to "cold walls".

Far slower to lose heat through an uninsulated wall than through an open window, for example.

listermint

GreeBo wrote: »

There is though, reducing the number of times the air is exchanged in your house will have a massive impact on your heating.
Once the air stops changing/escaping its far easier to heat this air and maintain that heat in your house, even if that heat is still being lost to "cold walls".

Far slower to lose heat through an uninsulated wall than through an open window, for example.

So we both agree both are necessary then....


yeah?

GreeBo

listermint wrote: »

So we both agree both are necessary then....


yeah?

Well depending on your goal you might need one much more than the other.

If I could only do one, or if I was to prioritize one it would be controlling air flow before adding more insulation.
You just cannot insulate away an air flow problem.

Muahahaha

Thanks for all the replies lads. Seems Im going to have to do a fair bit of research on this as whatever company I get out to quote will just try to sell me their solution regardless whether it will work or not. Had a dry lining company out earlier in the year and he suggested taking all the roof tiles off and insulating the roof proper at a cost of almost 6.5k :eek: So when the spray foam co. came out quoting 1.5k I thought it to be a lot more reasonable but its no use paying a cheaper price if it still isnt done right.

Im wondering is there any independent guidance documents out there from the likes of the NSAI or similar in regards to insulating an unusual attic such as this one or else what would be considered best practice? I know I definitely have an air tightness problem as the previous owner has shoved mounds of insulation near where the rafters meet the soffit/facia and I've seen other sections where there is daylight coming in here. Also a large birds nest in the attic tells me the same thing. Wondering is the junction between rafters and soffit supposed to be fully sealed and airtight? Or is there supposed to be a slim gap to allow airflow to ventilate the rafters and ceiling joists?

Lumen

It's not an unusual attic. There are probably hundreds of thousands of those in Ireland.

Not sure this is the latest.

https://www.engineersireland.ie/EngineersIreland/media/SiteMedia/groups/Divisions/civil/NSAI-Standard-Recommendation-S-R-No-105-of-2014-Code-of-Practice-for-the-Energy-Efficient-Retrofit-of-Dwellings.pdf?ext=.pdf

Muahahaha

Thanks Lumen, that document explains it clearly for me, specifically page 69 'Cold pitched roofs-insulation at rafters'.

One thing Im wondeirng though it does not mention anything about insulating the gable ends, both the exposed one (end of terrace) and the one adjoining my neighbour. I would have thought that it is important to have a continuous insulated envelope throughout the attic space? The gable ends are single block so no option for a cavity fill.

poker--addict

how big a difference will an extra layer of insulation make?

GreeBo

https://www.boards.ie/discussion/comment/118485294#Comment_118485294

It depends on whats already there.

Adding an 50mm to an existing 150mm probably wont do anything noticeable, adding 50mm where there is nothing will make a difference.

Adding 500mm badly will also do very little though.