Attic foam?

unkel

Hi, we had the attic converted 8 years ago. The low sides (outside the attic room space) were floored and insulated and the outside of the inner wall was insulated

However there are big gaps where the attic roof meets the floor and there is no insulation there at all. I can even see through to the outside at some places

Now my plan is to fill those gaps with some sort of expanding / insulating foam

Is that a good idea? If so, what stuff should I get and where can I buy it reasonably priced. If not, what would you do?

Fries-With-That

unkel wrote: »

Hi, we had the attic converted 8 years ago. The low sides (outside the attic room space) were floored and insulated and the outside of the inner wall was insulated

However there are big gaps where the attic roof meets the floor and there is no insulation there at all. I can even see through to the outside at some places

Now my plan is to fill those gaps with some sort of expanding / insulating foam

Is that a good idea? If so, what stuff should I get and where can I buy it reasonably priced. If not, what would you do?

Interesting information here.

https://www.google.ie/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CEcQFjAB&url=http%3A%2F%2Fwww.kingspaninsulation.ie%2Fgetattachment%2Ff2627aa0-96ef-4b10-9eeb-4e23abb4963e%2FWhite-paper--Loft-Insulation---Heat-loss-at-eaves.aspx%3Fdisposition%3Dattachment&ei=ZrNVUuuQI-vX7Ab1u4GIAg&usg=AFQjCNEowCRKVb31Eq8ZLDgCbF92p7tvrA&bvm=bv.53760139,d.ZGU

ravendude

Definitely not a good idea to cover the gaps.
The gaps are there by design, - they are required to allow the roof timbers to breath otherwise your roof will rot. The building regulations require 50mm where roofing felt is not breathabe (which is likely in your case).

ravendude

I have spent a (hell of a) lot of time making my dormer warmer, and we'll see in the forthcoming months, but its looking promising already.

Things I learnt
1/ Increase the insulation on the dormer knee walls. I have nearly 30cm of mineral wool on it now (200mm Knauf space blanket stapled over the existing fibreglas stuff)
2/ Block and tape where the knee wall meets the floor joists. ie. block in between each joist so cold air doesn't get into the living area of the dormer. I used foil bubble wrap cut to size and stapled it in between each joist, then taped. to help airtightness/
3/ Plenty of insulation where the knee wall meets the attic floor, again to prevent cold air getting under the dormer floorboards
4/ Look under sink and around all pipes (toilet, hot and cold water pipes). There is a good chance they have gaping holes. Seal these
5/ Hatch/Access doors. Insulate the backs of the these. Seal the edges with rubber seals, then tape over.


I still have to finish number 2 above, hopefully it will make a difference.

The dormer slopes seem by far to be the hardest to retrofit. I have 50mm of kingspan in the slopes, - I'd love more but it looks like I'll have to live with it. Could be worse I guess.

unkel

Some great tips, ravendude. The dormer knee walls in my attic are also the weakest link, they are far less insulated than yours were to start with!

batman1

I had the same issues with my dormer. In the end I done the following:

Removed all fibreglass from the crawlspace floor and behind the knee walls.
Fitted 4x2s onto every 3rd stud behind knee walls.
Fitted membrane across the back of the knee walls on top of the new timbers.
This was then filled with cellulose at high density.
Raised attic floor 8 inches.y r,i
Added 8 inches cellulose on top of existing fiberglass in the attic and floored on top.
Put 12 inches cellulose in crawlspace floor, maintaining required air gaps for ventilation.
Properly insulated and draughtproofed hatches.
The only area I couldn't get at was behind the sloping ceilings upstairs but the difference in the house is fantastic.

It worked out about the same cost as getting fibreglass rolls and tape etc etc

ravendude

As batman suggests also, - I think the key (if you are not using kingspan board, which is probably the proper solution, - this wasn't a viable option for me to retrofit due to cost and confined space) is getting enough depth in the insulation in the crawl spaces, both over the ceiling and the knee walls.
Both mineral wool and cellulose are not airtight (not necessarily a bad thing, to have it breath), - but you want it deep enough to hold some heat on windy days.
Insulating the absolute crap out of the hatch doors is vital also.

batman1

Insulating the absolute crap out of the hatch doors is vital also.

Very important. This was a big heat loss area for me.

Once the crawlspace area were completed I got 100mm rigid insulation board, cut it to the size of the hatch and then used foam around the edges. No more draughts and easy enough to remove if I ever needed access.

unkel

ravendude wrote: »

Insulating the absolute crap out of the hatch doors is vital also.

How do you guys go about that? My hatch doors have no insulation at all. I've bought some Knauf 100mm DIY base layer loft insulation roll and some heavy duty protective sheet (clear plastic)

Just a matter of stapling the sheet on the edges of the hatch door and filling it with the insulation material?

GreeBo

as above, dont seal these gaps up or you are asking for a moudly attic space.
Your attic is a cold zone and needs air flow to breathe. You insulate the floor/ceiling below to prevent heat escaping into this cold zone from the main house, dont try to keep your entire roof space warm unless its all heated (like the converted part)

ravendude

unkel wrote: »

How do you guys go about that? My hatch doors have no insulation at all. I've bought some Knauf 100mm DIY base layer loft insulation roll and some heavy duty protective sheet (clear plastic)

Just a matter of stapling the sheet on the edges of the hatch door and filling it with the insulation material?

Would probably be OK, - punch some small holes in the plastic though to let it breath. Knauf spaceblanket is basically this - ie. mineral wool "prewrapped" in perforated plastic (lets vapour through). Be careful with covering it insulation in plastic generally, if you're insulating the rest of the crawl spaces, - probably OK on just the hatch doors, - but if used more extensively plastic will trap condensation.
Also, I'd like more than 100mm of mineral wool to be honest - its not so much these days, but it all helps.

Screwing/sticking some kingspan board to the backs or fronts of the hatch doors might be easier (this is what I did, actually I have kingspan board both to the backs and fronts of the hatch doors and have taped up the edges of the doors to make it airtight), - but what you describe should help as well.

Its well worth the effort of going to town insulating the crawl spaces, - you'll see your money back in lower heating and also your comfort will be much better.