Thread: Spray foam

The home I inspected this morning has the spray foam insulation between the rafters in the attic. The foam is touching the flue pipes from the water heater and furnace. Is this allowable?

Tks
Jim

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Originally Posted by James Bohac

The foam is touching the flue pipes from the water heater and furnace. Is this allowable?

No. There must be at least a 1 inch minimum space between the insulation and the Type B gas vent.

Thanks,
I wasn't sure if the same rules applied to the spray foam. I have read alot about this but first time seing it installed. They even sprayed over the gable vents on the ends of the attic.

Jim

Originally Posted by James Bohac

They even sprayed over the gable vents on the ends of the attic.

Which is a 'good thing' when the insulation is at the roof sheathing.

Take a look at this website http://www.icynene.com/

If this is what you found, and most likely it is then you should read up on this product. The good the bad and the ugly..

Have you ever seen the ducts covered with foam?

Originally Posted by Rick Hurst

Have you ever seen the ducts covered with foam?

Ducts covered in foam might make sense in a traditonally insulated house where the insulation was in the ceiling joist area. You can buy flexible ducting in R-4, R-8, and I believe R-12.

If these ducts were sprayed in a home that was foam insulated (sealed system) - meaning designed for foam insulation, foam on the roof deck and exterior walls, no insulation in the ceiling.. then the attic area becomes heated space and you have no reason to use insulated ducts in heated space. Adding foam to the ducts is just a way to upsell the home owner.

Rick,

Yes. They use metal ducts then foam insulate them. What is the R-value? Don't know. However, if there is a weak area, or a tear or a hole, the cold duct (when used for a/c) could cause condensation to collect on the metal duct, which would then run down the outside of the duct (collecting inside the insulation where the insulation is not fully adhered to the metal), causing the metal to rust out.

I saw that problem a lot with fiberglass insulated metal ducts.

Darin,

Actually, insulating the ducts in a semi-conditioned attic where the insulation is on the underside of the roof sheathing makes perfect sense as it allows the air in the duct to have less heat loss/heat gain as the air travels through the duct, thus creating a more even environment throughout the house.

While on the subject of foam.

How not to patch an opening in the drywall. Came across this yesterday at a home of an 82yr. old gentleman that tried to patch up the hole the agent had asked him to fix.

rick

Well, excuuuuuse me, Rick ... I don't see no hole there.

Originally Posted by Jerry Peck

Actually, insulating the ducts in a semi-conditioned attic where the insulation is on the underside of the roof sheathing makes perfect sense as it allows the air in the duct to have less heat loss/heat gain as the air travels through the duct, thus creating a more even environment throughout the house.

I'd agree in non-AC or perhaps semi-AC space. I guess the differentiator between semi-AC space and AC space is a duct in the attic...

Hey Rick,

That would the great stuff applied in the hole.

Originally Posted by Jerry Peck

Rick,

Yes. They use metal ducts then foam insulate them. What is the R-value? Don't know. However, if there is a weak area, or a tear or a hole, the cold duct (when used for a/c) could cause condensation to collect on the metal duct, which would then run down the outside of the duct (collecting inside the insulation where the insulation is not fully adhered to the metal), causing the metal to rust out.

I saw that problem a lot with fiberglass insulated metal ducts.

Darin,

Actually, insulating the ducts in a semi-conditioned attic where the insulation is on the underside of the roof sheathing makes perfect sense as it allows the air in the duct to have less heat loss/heat gain as the air travels through the duct, thus creating a more even environment throughout the house.

Jerry,

I think there is some misunderstanding about conditioned vs semi conditioned. Once the insulation is applied, everything towards the living space is considered conditioned.

That being said, I think there is some benefit to insulating ducts even as they pass thru conditioned space, but when considering code you don't have to.

Originally Posted by Rod Butler

I think there is some misunderstanding about conditioned vs semi conditioned. Once the insulation is applied, everything towards the living space is considered conditioned.

Rod,

Yes, there is some misunderstanding, but not in my term use of semi-conditioned, but possibly in your understanding of what was being discussed and what the term means.

Originally Posted by James Bohac

The home I inspected this morning has the spray foam insulation between the rafters in the attic.

Thus the insulation is against the underside of the roof, which makes the attic within the thermal envelope, yet there is no conditioning being applied to that area. The conditioning (heating and cooling) is being applied to the living area below the ceiling.

Some call the attic in the above "conditioned", yet there is nothing being done to condition that area, other refer to that as "semi-conditioned" as that area is within the thermal envelope, is not being conditioned, yet is typically within a few degrees of the conditioned space as the temperature and vapors permeate through the drywall ceiling into the attic space.

I have noticed a trend of recent to go away from the term "semi-conditioned" and use the term "conditioned" for those attic areas, even though those attic areas are not being "conditioned". As with all newer construction techniques, names are brought into usage to describe something (in this case the unvented and sealed attic space within the thermal envelope) and then usage of that term is refined/changed to reflect a term which is more widely accepted.

10-15 years ago no one would have ever considered calling that attic "conditioned" unless and until you installed a supply and a return to that attic.

Today, "conditioned" is becoming more acceptable even though there is no supply or return and the attic is not being "conditioned". Back 10-15 years ago, and still in use today, was/is the term "semi-conditioned" as it accurately represents the fact that the attic was not being "conditioned" yet that the attic is assimilating itself to the conditions in the conditioned areas below it via transfers (temperature, humidity, vapor, etc.) through the drywall ceiling.

Anyway, that is why I used that term.

Originally Posted by Jerry Peck

Rod,


Anyway, that is why I used that term.

got it.

Originally Posted by Jerry Peck

Well, excuuuuuse me, Rick ... I don't see no hole there.

Yes and after further viewing and thinking an 82 year old fixed this . . . I'm thinking "not too bad old dude"!