# What is the proper way to insulate an attic furnace?



## enochian (Jul 1, 2015)

What is the proper way to insulate an attic furnace, when the rest of the attic is unfinished?


----------



## joecaption (Nov 30, 2011)

#1, We have no idea where you are because there's no location in your profile.
Most often just the ducts get insulated.


----------



## enochian (Jul 1, 2015)

Pennsylvania


----------



## Nealtw (Jun 22, 2017)

You want to protect the roof from heat or you could cause ice dams.
Insulated ducts like Joe said and very good venting to move any lost heat away.


----------



## Bud9051 (Nov 11, 2015)

Do you have enough room in that attic to build a room for the furnace, insulated and air sealed to keep the heat out of the cold attic.

Basically, if you can't contain the heat given off by that unit then you have to waste it to the outside to prevent snow melt and those resulting ice dams.

Bud


----------



## enochian (Jul 1, 2015)

The ducts are ductboard and are insulated as well.


----------



## enochian (Jul 1, 2015)

Bud9051 said:


> Do you have enough room in that attic to build a room for the furnace



I don't know if the truss system can handle the weight of drywall etc.

Plenty of space though.

Can you just use 2x3's and polyiso? Is polyiso allowed near an attic furnace without a thermal barrier?


----------



## Bud9051 (Nov 11, 2015)

Hard to build anything up ther with trusses and the furnace already there. An air barrier needs to be sealed and rigid and plastic does neither. Only thing that comes to mind is foil faced foam all taped up, if codes would allow it. They do sell duct board in 4x? sheets (I found 4'x10' near me) and it has a reasonable r-value. Plus it is basically rigid fiberglass insulation and not very heavy.

Bud


----------



## user_12345a (Nov 23, 2014)

I don't see a point of insulating the area where there's a furnace when the rest of the system, the ducts, have direct exposure.

to really save energy $$$ u you have to insulate the roof deck, but that's a lot of money up front.

otherwise just make sure everything is sealed up well and make sure the insulation on your ducts is a reasonable r-value, like r8.

it's not a smart place to put ducts or equipment, but once it's done, make the best of it.


----------

