Anyone know anything about foam roofs ?
Web site says they rock, but what are the downsides?
They offer a few kinds of spray foam insulation. Many houses can have it installed without doing anything to their existing roofs. It is similar to blown in insulation that is used in walls. Blown in insulation usually works pretty well. I would guess the downside is waiting 4 - 6 years before you break even on cost. Many people don’t stay in their house that long and it may not make as big a difference on selling price. If you had to replace your existing roof to have it installed, it may take a very long time to break even. You would have to need a new roof anyway to make it worthwhile. You have to weigh the cost against something like new windows which may provide similar benefits.
Web site says they rock, but what are the downsides?
Well, you have to start with (I guess) a flat roof.
The big downside as I see it is durability. I am sure they treat the plastic with UV inhibitors, but even then, relying on plastic exposed to full sun for years to not develop any cracks seems like a dangerous gamble.
I frankly don’t see any upside. I gather they are arguing that it reduces heat infiltration, but there seems other ways to combat that problem that are cheaper and more reliable than spraying plastic on the outside of the water barrier.
A roof is a system, not a thing. It has multiple parts and each part has a function and needs to be allowed to do it’s job well. If they all do, the roof works. The outer surface is a rain barrier. Concentrate on getting it to do it’s job as best it can. Insulation should be protected from the elements so it can do it’s job. Combining the two functions seems to me to result in a system that doesn’t do either as well as possible.
In some cases, there’s no other cosmetically acceptable way to insulate the ceiling. For example, Eichler homes (found in several communities in California) use post and beam construction. The ceiling is basically just the underside of the planks the roofing material is attached to. In other words, there’s no air space or attic between the ceiling and the roof.
As noted on the website, foam roofing can be applied to mid-slope roofs as well as flat ones. One of the photos looks like about a 3:12 pitch. In areas that don’t get much snow, flat to mid-pitch roofs are extremely common.
It can be used for low slope roofs as well, but certainly not for the pitched roofs on most houses. If you have a flat roofer with a tar and gravel roof, it might be a good choice.
As for how much of a gamble it is, it’s a method that’s been in use for 40 years, particularly for commercial roofing, and there’s enough of a baseline to show that the longevity is acceptable.
Some disadvantages:
It’s more expensive than flat roof alternatives such as tar and gravel.
You basically require a run of perfect weather to install a foam roof - the components are mixed and applied on site, and any moisture on the roof can compromise the installation, even condensation or high humidity.
Remarks concerning interior insulation rather than expecting the roof to do the job apply if the building design permits it. Foam roofs are popular for things like old Eichler style houses that don’t have any way to install traditional interior insulation without major reconstruction.
ETA:
crossed previous poster, who made some of the same points.
Yeah I have an Eichler style house with a flat roof and no insulation. I have a contractor who says they CAN put insulation in with a new roof, I think they’re gonna raise the roof up a bit to make room for some insulation basically.
But saw this alternative. The person who told me about it said it was about $4/sq foot… which would make it about $6,000 cheaper than reroofing the way we were planning on doing it. I have not confirmed the cost, as it’s the weekend, but was gonna check on Mon.
So… as we have the ideal roof for this situation, and we’ve got the right weather in SoCal summertime… if the price is similar, is there a strong advantage over going foam versus reroofing? Ignoring the cost for the moment, as I now have conflicting info as to weather it’s cheaper or more expensive.
Just for the sake of keeping my house cooler in the summer (and warmer in the winter, though that’s less of a problem), any suggestions as to which way to go?