Insulating Attic Crawl Space

Doge

Hi guys, first of all I'd like to say I appreciate all the users on here who go out of their way to share knowledge and advice on this forum.

Im just looking for advice on preventing drafts and insulating our attic, whilst keeping airflow so the rafters etc.. do not rot.

So when we bought our current house the attic was already converted but not insulated properly in the 2 crawl spaces that run behind the plasterboard walls. So as you can imagine it gets really cold up there in the winter.

It is the slant of the roof which was not insulated at all in the crawl spaces.

The crawlspaces are accessible via cabinet doors.

We are currently doing renovations in the house and had Xtratherm insulation slabs, 2 inch? insulation slabs with palsterboard, and also a lot of glass wool insulation left over so decided to put it to use in the attic.

Here is how the crawl space currently looks on the right hand side:







This is the better side, as you can see it is covered by a chipboard floor, and already had a plasterboard wall to the left with wool insulation inside (i checked to make sure)

As you can see we have used up all of our xtratherm insulation and made it a priority to cover the far half of the roof, as that is the end where people will be using the attic.






Now here is how the crawl space on the left hand side currently looks:





We had to put down flooring from left over timber and also screw the 2 inch insulation slabs with plasterboard to the right of the crawl space, leaving a gap where the tank is. The walls around the tank are insulated btw.





There is an overflow pipe for the tank going down the slant and out though a hole, and as you can see by the light getting through it is a source for a draft.







Im not sure how we can seal the hole around the overflow pipe as its quite a reach down and we dont have a ladder long enough to do it from the outside.

As you can see the bottom end of the slant of the roof that goes up to the horizontal rafters is not insulated at all along both sides of the house.

Is there any way of insulating this with glass wool insulation whilst maintaining airflow? Or can you only insulate across the horizontal rafters?

If anyone could give guidance on this, I would really appreciate it.

Thanks for your time.

Doge

Doge wrote: »

There is an overflow pipe for the tank going down the slant and out though a hole, and as you can see by the light getting through it is a source for a draft.

A friend of mine has just suggested using one of the xtratherm slabs and cutting a channel into it that will allow the pipe to go through the slab, to try and block the draft caused by that hole for the pipe.

So far that sounds like a good idea to eliminate the draft caused by that hole.

They also suggested pushing the xtratherm down further into the slant so that only about an inch or 2 of it goes past the floorboards.

MicktheMan

To be totally honest with you, I doubt what you are doing will make a blind bit of difference to the draughts or heat loss. Insulation, in the main, does not address air leakage or draughts.
The NSAI have published quite a good guide which you should perhaps read before proceeding. If you google "nsai s.r.54" you should find it online.

Metric Tensor

There's quite an "interesting" range of insulation techniques going on there OP!!!

Just to point out that your roofing felt appears to be the old fashioned "impermeable" heavy black kind - with this type of felt you need to provide ventilation to the rafters underneath either via vent tiles or through vents in the soffit. There should be a gap for this ventilation directly under the roofing felt. This means that if you are placing insulation on the sloped section of your roof there should be a two inch continuous gap between that insulation and the roof to prevent the rafters from excess condensation and eventual rot. This gap needs to be ventilated by one of the two methods I mentioned above.

You may have left that gap but it's hard to tell from the photos.

Buck Turgidson

To my mind op you should be treating the crawl spaces as the exterior of the house. They are not occupied or heated, so you should concentrate on stopping heat escaping into them from your occupied areas. Insulation on sloping roof is pointless.
Extra insulation on crawl space floor, and vertical wall of attic living area, and
the access doors would be my way to go. Be sure to protect water tank and pipes from freezing. Good luck with it!

Doge

Thanks a lot for all the helpful replies, you guys are awesome!

Calahonda52

MicktheMan wrote: »

To be totally honest with you, I doubt what you are doing will make a blind bit of difference to the draughts or heat loss. Insulation, in the main, does not address air leakage or draughts.
The NSAI have published quite a good guide which you should perhaps read before proceeding. If you google "nsai s.r.54" you should find it online.

https://www.nsai.ie/S-R-54-2014-Code-of-Practice.aspx

Doge wrote: »

Thanks a lot for all the helpful replies, you guys are awesome!

Not half as awesome as the pics.

Just to add to what has been said already, a critical point here is the clearly visible access for cold air to pass across under the flooring between the knee walls from one side to the other, negating to a greater or lesser extent the value of any insulation therein.
So where all these pipes go in...

The other point for the soft insulation materials, if air can pass through them then they are worthless.
Also if you stuff them in really hard, pushing out all the air, they are equally worthless.

air

Good advice above.
The insulation in the sloping sections is achieving nothing whatsoever at the moment.
You have the choice of either insulating the eaves properly (which is pointless unless you want to use the crawl space) or insulating the vertical stud walls from the crawl space side.

Either way you need to do it to a good standard for it to be effective.
I insulated my attic right down to the eaves but I plan to use the eaves area for storage so they will be heated.
I used 100mm foil backed PIR foam cut to to fit each gap and sealed it with expanding foam before trimming the excess and then foil taping over the join. I then fixed another 50mm sheet across the rafters and taped that up again.
Very time consuming but there's no point fitting insulation incorrectly, it won't do anything.

air

Oh and with regard to the pipe being a source for a draught, I wouldn't worry about it at the moment, every bit of exposed felt is currently a draught source.

Doge

I guess the only consolation is that by putting the insulation up there, it saved it all from going into a skip! :pac:

It was literally just left over insulation we had from the kitchen.

I guess it wasnt a total waste of time though, that 2 inch insulation we put in the right hand side of the left hand crawl space was badly needed.

Learned a lot from this thread already!