Spray-foam insulation makes homes unable to be mortgaged

There's a whole class of corrosion in metal structures called Corrosion Under Insulation or CUI. This is a problem for any insulated metal structure, but it is way worse with spray foam because the foam traps moisture very effectively, when it breaks down it becomes acidic, it is difficult to remove for inspection or repair, and it makes hotwork dangerous because it is flammable.

When I started seeing wooden houses and roof decks get spray foamed, I could only think that these structures will likely be rotten and useless in 20-30 years. I would only sprayfoam something if the substrate is completely impervious to moisture, like if it was fiberglass or something. Even then you're likely looking forward to a pretty evil concoction under that insulation in a decade or so.

Moisture barrier: It blocks water vapor and prevents mold growth by reducing humidity levels in crawl spaces and other areas.

Structural strength: It can double the racking load of a home, making it more resistant to severe weather. Air sealing: It protects against drafts, cold spots, and uneven heating.

Longevity: It retains its R-value over time and can last for decades if installed correctly. Energy cost savings: It reduces your carbon footprint by consuming less energy.

Improved air quality: It doesn't contain harmful micro substances like fiberglass insulation.

The reason it's nonsense is that the side covered with foam (especially closed cell) is now protected by waterproof polyurethane. Water isn't getting to that side.

The other side is now insulated from the inside, so that isn't getting things like condensation because the temperature differences should be negligible. If people think about a cheap styrofoam cooler, it's cold on the inside and there isn't condensation on the outside on a humid summer day. The outside isn't cold, that's the point, so condensation doesn't happen there.

Then maybe someone would say if there was a roof leak the wood would get wet and rot, but that would happen anyway. That's a major disaster and foam won't cause any more problems than are already happening.

Implementation details matter. From the OP's article:

> At the root of the problem are cowboy traders who apply the foam without a full survey or appropriate expertise – but because of lenders’ caution, this is affecting other homeowners who had similar work.

One potential problem that could occur is ridge rot:

> Lots of attics insulated with open cell low density spray foam (Photograph 1, Photograph 2 and Photograph 3) are having problems – in hot humid climates, mixed humid climates, and cold climates. The problems are moisture related. The attics are “unvented” – open cell low density spray foam is installed directly on the underside of roof sheathing. The attics are humid. Very humid. Unacceptably humid. And the humidity collects at the upper portion of the attics.

* https://buildingscience.com/documents/building-science-insig...

> When you spray ocSPF into wall cavities from the interior the ocSPF can act as the air control layer and thermal control layer. It can’t act as the vapor control layer – it is too vapor open. This is a problem when you spray ocSPF on the underside of roof/attic assemblies you can end up with problems (“Ping Pong Water”).

* https://buildingscience.com/documents/building-science-insig...

And we've long had governments that take a hands-off, laissez-faire attitude - expecting the market to sort things out. As they see it, this insulation can be done properly, building owners chose to buy it, why ban a promising new green technology when the UK has millions of under-insulated homes and an energy price crisis?

Similarly, the UK has a load of tower blocks clad in flammable insulation after vendors Kingspan and Celotex scammed their way through fire safety testing - but somehow all the people who made money off it have disappeared and the taxpayer has to pay to remediate it.

Because tbe lenders are at risk here, they won't lend unless you do the removal so that the lender can inspect.

It's not unsellable, there are a lot of private buyers, both investors who intend to rent it out and people with significant money looking to just buy outright. For example my mother moved long after retiring, obviously she can't get a mortgage, so she paid cash. However, if a mortgage will be hard to get this makes it significantly harder to find a buyer, especially if your ideal buyer is younger and not wealthy. This can depress prices.

Closed cell foam is the best insulation - if it is installed correctly. You should want it as it is the best insulation. However the payoff is several decades vs much cheaper insulation and so most people find it isn't worth the costs.

In general, for most houses, putting in the most cheap insulation you can, and then investing in a heat pump is the most bang for the buck and better for the earth than the most foam you can and then using a much less efficient HVAC system (in a new house this is typically what code requires, but there are a lot of old houses with minimal insulation and a terrible furnace).

Also why couldn’t they afford them? Is this the US where the equivalent of a $5000 system elsewhere in the world seems to cost $25K to install for some reason? Even then, with depreciation as long as it’s a couple of years old surely the residual value isn’t that much…?

Otherwise why not sell them for $9.99 along with the house?

> Executive found that condensation could cause 25% of roof timber to decay within five years if spray foam is applied directly to roof tiles, or certain underlays. The general risks increase the further north the property is, because of colder climates.

Most houses in the UK will have a timber frame, condensation will cause the wood to rot.

When using any type of insulation in places where temperatures can vary and humidity can get high you should always ensure the wooden parts have enough room to breathe (e.g. 10cm of empty space above them if the insulation is at the bottom).

Also if you want insulate an old house consider you should install an HVAC system so that you are properly venting. Old houses self ventilate because they’re so loose compared to modern homes with tight envelopes.

The above is my current belief. Who knows if I'm right.