Attic insulation - spray foam

[ash_scotland88]

So part of getting the boiler loan we have to insulate the attic, wasn't much of a biggy as we eventually planned to.

Thing is we're feeling time sensitive and originally would have been down by us / at our leasure and Home Energy Scotland stipulates it has to be done by a professional or a home report redone once it's done.

 

Most companies appear to only offer spray foam as a solution. I have concerns regarding condensation and ventilation as it won't offer the 50mm gap.

What are peoples thoughts? It can't be that bad an option if companies are still going.

[Jilly]

I've heard terrible things about the spray stuff.  If you have bituminous roofing felt, you are right, it needs a 50m breather gap. 

[ash_scotland88]

Roof is pitched with a flat central area that is covered in rubber.

Been doing some reading and we're clay tiles which is not ideal either.

[MAB]

One of the big issues with spray foam insulation is when you come to sell a property.....

 

"Whilst contractors may push the benefits of spray foam, lenders will often insist that surveyors take a different view. Surveyors and valuers will often have to discount the value of a property or request a specialist report, because it has SPF insulation. It may even make a property unmortgageable in the eyes of a lender."

https://sdlsurveying.co.uk/news/surveyors-blog-valuation-considerations-of-spray-foam-in-roofspaces/

Edited June 23, 2021 by MAB

[ash_scotland88]

That's the same article I've seen.

 

It's hard to find positive articles that are not posted by spray foam suppliers.

[Lorenz]

I am renting a house with spray foam insulation. It is a concern if we were to buy it, and as has been pointed out, if we could indeed get a mortgage on it. But it is a poorly done thing amongst old oak beams and leaks air like a sieve! Unless a building was outstanding in some way it would put me off buying it, especially the extra cost of any roof works, and it has often been used to cover up rotting timbers and indeed may encourage rot.

[George]

No no no no, don't use spray foam on roofs.

 

A lot of spray foam companies should be shut down for fraud.

 

You should be able to find a roofer or general builder to install pitched roof insulation, the required detail can be given by Kingspan or similar, or by an architectural technician.

 

 

[Temp]

+1 

 

Does the insulation have to be at rafter level? or can it be on the floor of your attic at joist  level? Eg are there rooms in the roof?

[ash_scotland88]

I have totally ruled out spray foam.

 

Had a few companies out today, last one was a general builder who is quoting for insulation between rafters.

 

The attic, and I've actually made a thread before, is a walk up; a door and stairs. It's also floored with original (1930s) tongue and groove flooring, so pretty tough to remove. The other thought I had was blow in insulation between the joists. There's a gap around the edge where the tube may hopefully fit through and if we have to we'll remove a row or two to allow better fill.

 

Either way, without totally change of the attic we can't get the recommended 270mm in one layer.

[ash_scotland88]

Had a costs to install PIR through which is fractionally cheaper than spray foam at 3450. 2/3rds is the board costs looking at an online calculator.

It is something we could do, at our leasure, but our leasure time feels like it's greatly decreasing before end of August/September onset of autumn deadline.

[trialuser]

Similarly, but different...

Because of a cock up installing my tony tray (Flapped in the gales, ripped to shreds and now cut off), I need to find a way to insulate and make airtight the first floor zone between the ground and first floors. The joists are 305mm posijoists. It will be tricky to cut foam and fit insulation between and across the ends of ths pozi's, so I was thinking about spray foaming just the joist zone around the perimeter. Does anyone have any ideas on whether this would work?

Thanks

[jfb]

4 hours ago, trialuser said:

Does anyone have any ideas on whether this would work?

You can get tape that sticks to the timber and then you render over the bit of tape on the wall for airtightness.

 

Why not use glassfibre or rockwool? Much easier to fit than rigid baords.

[Iceverge]

1 hour ago, jfb said:

You can get tape that sticks to the timber and then you render over the bit of tape on the wall for airtightness.

 

Why not use glassfibre or rockwool? Much easier to fit than rigid baords.

I agree with this for OP and @trialuser. 

 

AIrtight foam for the gaps and airtight paint over the top around the joists. 

 

what U value are you targeting @ash_scotland88. How deep are your rafters?

 

[ash_scotland88]

1 hour ago, Iceverge said:

I agree with this for OP and @trialuser. 

 

AIrtight foam for the gaps and airtight paint over the top around the joists. 

 

what U value are you targeting @ash_scotland88. How deep are your rafters?

 

 

Rafters are only 150mm.

 

Can't remember figures off my head but it started as trying to achieve 270mm to be eligible for the home energy Scotland boiler loan.

 

May also add some under floor insulation at some point too.

[trialuser]

5 hours ago, jfb said:

You can get tape that sticks to the timber and then you render over the bit of tape on the wall for airtightness.

 

Why not use glassfibre or rockwool? Much easier to fit than rigid baords.

I am talking about the area between the plasterboard ceiling of the ground floor and the egger chipboard floor of the first floor in a timber frame build, so not normally rendered. It's a strip around the perimeter of the building within the depth of the posijoists. I could stuff in rockwool but I dont think that will deal with the airtightness. Taping would be a nightmare, posi's are on 400 centres and are from memory about 122 wide, so about 60+ small 300mm x 280mm voids and the ends of the posi's ideally want a bit of insulation as well

Thanks

[trialuser]

Google just found this photo of what I'm hoping to diy

https://www.facebook.com/prizesprayingltd/photos/pcb.3692954434167072/3692943657501483

[SteamyTea]

Have you looked at the price of a new boiler without using the loan scheme. It may work out cheaper.

[ash_scotland88]

1 hour ago, SteamyTea said:

Have you looked at the price of a new boiler without using the loan scheme. It may work out cheaper.

They quoted as private pay.

The way the scheme works, I believe, is that the fund flow through the individual. And they (agency) just required a quote from a business.

It's an interest free loan, not free money for an individual to claim for, so I'd imagine they won't be jacking up prices anyway.

[Iceverge]

On 04/07/2021 at 22:45, trialuser said:

I am talking about the area between the plasterboard ceiling of the ground floor and the egger chipboard floor of the first floor in a timber frame build, so not normally rendered. It's a strip around the perimeter of the building within the depth of the posijoists. I could stuff in rockwool but I dont think that will deal with the airtightness. Taping would be a nightmare, posi's are on 400 centres and are from memory about 122 wide, so about 60+ small 300mm x 280mm voids and the ends of the posi's ideally want a bit of insulation as well

Thanks

our tony tray was destroyed by the wind too.

 

rectified with sand and cement for the larger gaps followed by airtight expanding foam and then airtight paint, 

 

it was slow but achieved a very ACH good result.

 

If you could get someone to spray apply blower proof paint it would be quite quick.

[Iceverge]

On 05/07/2021 at 15:40, ash_scotland88 said:

They quoted as private pay.

The way the scheme works, I believe, is that the fund flow through the individual. And they (agency) just required a quote from a business.

It's an interest free loan, not free money for an individual to claim for, so I'd imagine they won't be jacking up prices anyway.

It sounds easier to just pay for the boiler