Spray foam insulation

Anyone tried it? Looking into options for the barn conversion.

The big issue is that there will be no air gap but I actually think that might be a good thing as air gap = condensation + mould etc and needs ventilated. Insulation right up against the wall = no gap but will it affect the wall long term? Walls have been re-pointed in cement mortar so there is actually less chance of water ingress compared to lime and most stones is solid stuff but I am under no illusions of the power of water and I did spot a few of the more porous red (sandstone?) ones on the surface.

In all honesty I quite like the idea and not done the calcs yet but looking at 75-100mm on the walls and 200-250mm in the ceilings. South side will be mainly glazed so need to make it up elsewhere.

no idea re houses but it is widely used in narrow boat building and it works very well in that application

Yeah I had seen that. Is that on both metal and wooden parts then?

just thought I better add, will be fitting one of those heat recovery ventilation systems to manage internal moisture and cooking smells, bathrooms etc. due to open ceilings will probably have one doing the main living area/kitchen and utility and then another doing the bathrooms and bedrooms. Not worked out the unit sizes and costs yet, just collecting ideas and identifying hurdles.

yes both metal and wood
Essentially they fit a wooden frame – that the internal wood, often ply wood will attach to – and sprayfoam the lot of it and then just trim as required.

I’m not an expert, but here is my train of thought…

In post 1 I was worried that you dismissed condensation. Gap or not, the moisture has to go somewhere. Invariably it will go somewhere annoying, and difficult to deal with.

In post 3, you say you’ll be using MHRV, and I’m no longer worried. A good system will keep the humidity down to a level that will not be a problem.

Well I kind of figured if we are leaving a gap we have to batten it out with metal (will eventually rust) or wood (will eventually rot) as we will get condensation in the gap. If we use spray foam we can space the battens off the wall (and in doing so get it nice and plumb) with some non-rotting plastic spacers and then the foam will fill the gaps behind and secure and encase the battens up to them being flush on the surface and ready for covering with plasterboard/insulated plasterboard.

MHRV (that’s the badger) – something I am including from day 1 for a number of reasons. Budget so far for heating and PV s quite large but makes sense taking advantage of RHI and FIT, but without which the technology would probably be cheaper but that’s another discussion.

Just a note on the pointing, without knowing the specifics, replacing a lime mortar with an OPC mortar is not usually a good thing as you’ll end up trapping moisture in the masonry, leading to damp and stone decay. Working with lime can seem a pain, but can utterly transform an old building when done properly.

I’ve got lime plaster on my flat and it’s transformed the place. If I was going for natural build I would go full on breathable with lime mortar etc but this place just doesnt lend itself to that. Lime mortar would be a problem with the spray foam as it will let lots of water in but then it will have no place to go.

It’s 6 of one and half a dozen of the other at the moment. My preference is for a nice breathable, sustainable building but I seem to be going in completely the opposite direction at the moment. I just want to move somewhere nice and warm where you can make a house of mud…

Might be worth having a chat with these guys[/url].

Apparently they do a BASF SOFI which is breathable (suitable for use straight onto wooden sarking in a roof at any rate)

Just had ours done last week. Noticeable difference in both temperature and weather noise in the upstairs (loft-ish with dormer window) rooms. They’re very helpful and their work is pretty tidy too.

Cheers, Scruff

Andy is definitely be looking out asking on navitron – I’m looking at doing a similar conversion and they’re really helpful.

Thanks for the links, I know BASF very well so interesting to see their products. Have sent an initial enquiry to a place I found through random googling but that site has more info and data sheets appeal to me 🙂

Think I might be wasting hours reading stuff on that forum too.

The more I look into it the more I think the spray foam makes sense. We can have complete floor to ceiling insulation up the North side of the building. It is in a flood plane too (I know bad idea etc but very low risk and on the edge of the plane, 1m above the EA limit and never flooded) so the foam actually makes a lot more sense. The rest of the building will be designed with flood defences on the openings and so that should the worst happen it will be easy to clean out (possibly put pumping points in), all the expensive stuff like the GSHP will be elevated and the walls will be done so that plasterboard up to 1m is easy to remove and replace. As you can see I am preparing the flood management document for the council! Just hope the house insurance people like it too.

Video I watched the other day:

Bit easier than using DIY aerosols 😀

Whatever product you choose be sure to look for independent testing and that it is installed as tested. I always look up bbacerts.com, saves false advertising nonsense.

If the barn is old enough to have been built with lime mortar, pointing etc with modern cement will subsequently damage the wall.
Following on from above, if those walls are old enough and have lime holding them together, backing them with an impermeable material will cause problems as moisture migrates through, or rather doesn’t when it meets the spray foam.

You should really get some professional advice as the clash of ancient and modern needs consideration and careful planning.

I do a lot of work with PUs so I know how easy it is for them to mess up. Will remember to check them out properly.

sharkbait spotted your thread on that forum. This site is quite useful for quick checks: http://www.vesma.com/tutorial/uvalue01/uvalue01.htm

My current wall design is coming out as 0.21 W/m^2K.

One of the first consultancy jobs I had in composites was designing thermal models for huge composite ovens (10’s of meters long) so I will dig out my notes from them and build a whole thermal model for the house. I even include things like free/forced convection losses, every little thermal bridge, leakage, radiation etc etc. Takes a lot of hours of whittling away on the fine details but my models were very close to the actual thermocouple readings and power ratings when applied to the old ovens before we designed the new ones. I even told them how much heat went into the concrete floor where the feet stood and how much the wall heated up on the other side of the factory.

If you’re used to modeling etc, you might want to have a play with WUFI. It is used by a few of the real wall and building geeks I know. Good for moisture and thermal.

https://wufi.de/en/software/product-overview/%5B/url%5D