Information regarding condensation/ attic foam insulation and ventilation,

  • Recently I did an inspection near Galveston ( ( beach) , very hot outside aprox 96 deg F, And found and attic that was insulated with foam on roof deck and attic walls to exterior, with no visible ventilation .soffits, ridge nor vents ( Am aware of the 1/150th of ventilation, or 1/300 in some cases recommended for attics) , its the second attic I found this way, the other was insulated with bat type insulation, but also had no ventilation. Are there any other type of ventilation used for this type of insulated attics?. Also the property in Galveston has lots of condensation coming out of ducts system with A/C working, I think it was due to no attic ventilation?

Carlos Orellana

Someone is trying to create a “conditioned attic” as recommended by Dr. Joe Lstiburek (Phd building scientist and principal at Building Science Corp). This concept has been used with success firstly in the “Build America” program and is now spreading into general use.

From your pictures, this attic is not properly insulated/sealed nor are the ducts all fully/properly insulated…this system was doomed for failure. Attic ventilation may make the problem worse and will certainly increase air conditioning costs!!

The other attic you mentioned with batts on the inside roof deck may be worse than this one!!

I inspected a home this week with this type insulation. The builder used a product called Icynene, a water-borne spray foam insulation akin to what you use to seal around wall plugs and such.

Did some research and also called a local dealer for info. They recommend a minimum of 5" applied to the bottom side of the decking, a barrier wall between the garage (if any) and the Living area of the home, no insulation at all on the ceiling, and an air-tight attic. They claim double insulation will lead to condensation and mold; I can see that, but not if it’s properly vented.

The house had an average of 4", not 5" and as little as 1 1/2" on the barrier wall between living space and garage.

Now, the kicker. The Icynene has an “R” of 3.6 per inch of thickness, but according to the literature and the dealer, it performs to an equivalent “R” of 6. This supposedly due to the fact it seals off all air infiltration.

The attic was about 105 degrees; nothing between the attic and the living area but 5/8 drywall…doesn’t add up to me.

I’m not sold on a sealed attic and hot ceiling.

i live in orange about hour and a half from galveston. i have foam in the walls closed cell and attic open cell. attic highest temp has been 81 so far this month humidity is around 50%.

Are there any issues with having exposed foam in the attic? In particular those related to fire?

Exposed foams must have a flame spread index of 75 and shall have a smoke-developed index of not more than 450when tested at a maximum thickness of 4" per ASTM E 84

Thank you Mr. Tyson.
One note. Maybe just my view.
A link to ASTM E 84 and the rest of your quote.
Thank you for your useful information.
Questions on foam , how to, and where to are being asked more and more in my area. Montreal Quebec.
http://www.astm.org/Standards/E84.htm