I've been pondering over whether boarding internally with insulated PB is worth doing and paying for on my build, looking for advice from the knowledgeable folk of BH.

 

The build up is Fibolite Block, 90mm PIR, Brick.  The guys did a decent job with the install of the PIR from what I could tell but reading the odd tale of woe here and there has made me think on a bit.

 

If I had a time capsule I'd have built with a wider cavity, but he who goes along with drawing and basic regs without knowledge repents!  So to improve and build a more comfortable house with lower running costs to live in, is it worth the outlay now.  No issue with the capital spend now, I'll just have to suck it up and push the finish date back a month or 3.  I'm not clever enough to work out running costs and ROI time against the cost of insulation so I'm sticking my finger in the air and gauging some opinion.

 

I was thinking of 37.5 or 42.5 boards.

 

Any thoughts

Probably into the arena of diminishing returns, plus you want to keep the thermal mass (I know, I know) of the blockwork exposed to the internal environment. 

6 hours ago, George said:

Probably into the arena of diminishing returns, plus you want to keep the thermal mass (I know, I know) of the blockwork exposed to the internal environment. 

Hope all well at your end George.

 

The thermal mass thing seems to out of favour on BH at the moment. But yes I think you are hinting at how a Trombe wall works.. and that will play havoc with standard software! Spot on George.

Focus on airtightness if you can. 

 

It's the cheapest win. 

 

Thereafter more insulation. 

 

My neighbour did PIR boards with the residual cavity pumped with closed cell foam. I think it was fairly successful. 

Yeah, airtightness is one of those ongoing jobs we are working on as we progress, windows and doors have started going in this week so this will help us hunt out air leakages.