Thermal imaging

[tobydog]

Our small village is doing a great job at trying to go green. Quite a few of us planned to help the village by investing in PV panels for the village hall that would provide electricity for the hall and community store, plus income from the feed-in tariff. We would share in the profits from the feed-in tariff with the intention that we only broke even. Fair enough. All was going well until the government moved the goal posts at the end of last year on the feed-in tariff rates and our plans were scuppered. We are still going ahead and the green group is now asking for donations towards the cost. Hopefully we'll get there.

As part of a general update in the hall at the weekend, we were offered a free thermal image of our homes to see where we leaked heat. I was thinking of having this done anyway before I start on insulating the walls. Although we have 9" solid walls on three sides downstairs, the front and top is timber framed. The front has the thermal efficiency of paper and comprises cement render, 3" of badly fitted loft type insultation, and gypsum panelling. I will be taking the gypsum off and filling the voids properly with sheeps wool (or equivalent) and then refit breathable panels. My only problem is sourcing breathable panels the same thickness as standard gypsum boarding because the depth I have to work with is very limited. Any ideas?

I will let you know how I get on and try and post some of the thermal images if possible.

 

[Zebra]

My only problem is sourcing breathable panels the same thickness as standard gypsum boarding because the depth I have to work with is very limited. Any ideas?

Don't know if this is at all helpful but woodwool board comes in 15mm thickness for interior use, which is not much thicker than 12mm plasterboard. I've bought a pile of it from Ty Mawr in Wales - that was the cheapest source I could find. But with your cement render on, is it necessary to have breathable boarding on the inside? There may be the risk that interstitial condensation would occur on the inside of the cement render.
Having said that, I have heard it said that interstitial condensation from diffusion through the building fabric is rare, and much more likely to be caused by air leakage where the airtightness detailing is not good enough (as I have found to my cost....). In your situation it sounds like it would be very important to have a good airtightness layer on the inside of the frame to prevent air leakage into the gap between the studs, which could then condense there.
When I was doing calculations for my timber frame, the company that supplied the sheepswool were incredibly helpful, and did all sorts of dewpoint calculations for me with a variety of different build-ups. I can give you the contact details of the person I spoke to if that helps.

 

[tobydog]

Thanks Zebra, the contact details would be helpful. The problem I have is that the gypsum panels currently fit perfectly in some sections of the house and not in others. Where they don't, the top of the panels simply disappear up into a void where moisture probably gets in behind them anyway. This would be awkward to fix but no impossible. With cement on the outside (and not going anywhere anytime soon) my thinking is to have the voids breath to the inside the house where to some degree I can control ventilation. I did remove a corner section of one of the sealed panels above the sole plate to check if there was any rot going on. It was absolutely fine and just the insulation was rubbish. I'm hoping that any moisture that may find it's way behind a woodwool panel and into sheeps wool, can be contained and easily find it's way out again. I'll have a look on Ty Mawr's site. Thanks

 

[Zebra]

I'll send you a PM

 

[tobydog]

Thanks Zebra. Regarding the woodwool, I've looked at this before and was slightly put off when Ty Mawr described it as wood fibres bound together by a small amount of Portland cement, and also being waterproof and damp proof. I kept looking for the word 'breathable' but didnt see it. Maybe it's just this make. I may need to look elsewhere anyway because even at 15mm, they will still need skimming with a lime top coat. The studs in the timber frame in question are so wiggly wobbly and one at least actually looks like a big branch! Even the gypsum board already stands proud of the studs in some places and I need something around 10mm and rather bendy. To the builder who ruined my wall, please can I have my wattle and daub back

 

[El Greyo]

I believe Ty Mawr's wool-wood boards are breathable, at least we bought them on that basis and I did speak to Ty Mawr about them at some length. But yes, they do need a layer of lime plaster. They aren't flexible but are easy to cut to shape. Not really knowing your situation, I'm not sure how suitable they would be or not.

 

[Zebra]

Yes they are breathable, but I can see that they may be too thick. Laths on battens? Probably no thinner. Expanded metal lath, dare I say it? Not sure how this would work though, in terms of fixing and type of plaster to use.