Thermal distortion and your old house

By: Conrad Neuf , Contributing Writer
In: Old House Inspection, Old Houses, Old House Construction, Home Improvement Tips, Old House Musings, In The News

One of the things I’ve always liked about the construction industry is that no matter how long you’ve been in it, you can always learn something new. My lesson today was on thermal distortion. Most people know that vinyl siding can melt–and if they don’t, they soon find out when the grill gets too close to the siding on the rear patio. I wish I had a dollar for every time I’ve been in a homeowner’s rear yard and had them ask me why their siding was distorted in a particular area. It was usually obvious they had moved the grill and were hoping I’d fall for the old it’s-defective-siding ploy.

Thermal Distortion--photo from greenbuildingadvisor.com

Thermal Distortion--photo from greenbuildingadvisor.com

I was talking to a siding salesman today and evidently thermal distortion has turned into a big problem with vinyl-sided homes across the country. It seems to be of the same proportions as the problems we had with certain types of stucco a few years ago and roof sheathing back during the ’80s. Modern windows have become so good at reflecting the sun’s heat that they’re melting the siding on neighbors’ homes. It’s similar to the principle you demonstrated when you were in the Girl Scouts or Boy Scouts and used a mirror to burn clumps of grass.

Who’s to blame for thermal distortion?

One of the problems with the thermal distortion fiasco is that no one seems to be worthy of blame. Most vinyl siding is designed to resist deflection up to around 160-170 degrees, which has been fine in most situations. Window companies are doing their best to make their products more energy efficient and to provide homeowners with lower cooling costs. Unfortunately, when the two products are put in close proximity thermal distortion can result.

Who's At Fault?--photo from greenbuildingadvisor.com


Most of the episodes reported seem to be occurring in newer communities where the homes have been built on top of each other. However, I can also see it becoming a problem in towns where old houses are close and owners are restoring their homes with vinyl siding and high efficiency windows. There’s no doubt in my mind that if my neighbors installed windows with upgraded Low-E coatings, the reflected heat from the summer sun would be enough to melt vinyl siding on my home. It will never be an issue, however, as my old house will always have wood siding.What’s the solution? The siding salesman told me his company had developed a siding panel capable of withstanding 220 degrees, but it must still be in the testing stage, as I don’t see it on their website. Other possible solutions include telling your neighbor with reflective-coated windows to keep screens on their windows or to plant shrubs between your homes.The lesson here is that if you’re thinking about putting vinyl siding on your old house or you see your neighbor installing new windows, keep thermal distortion in mind.