Recently learned regret about heating my house.....

[NM_Shooter]

The things that I learn from experience. 

I built an addition on my house about 10 years ago or so, and in that addition, I have a lofted ceiling room that is about 25x40.  I put a large Harman stove in it, and that stove works pretty doggone well.  So well in fact, that I have to turn the damper down low almost as soon as I start the fire or the room goes to 80 degrees in two hours.  I've taken to putting a large box fan near the stove to push warm air out a door and into other parts of the house. 

We've been known to have to throw away some of that heat by opening a door in the back.

Had I been smart, I would have installed a duct from that room into my central A/C handler to push warm air around the house.  My house has in floor radiant heat, so the A/C is the only ducted air that I have. 

It sure would be nice to move that cheap heat around.  I haven't completely excluded the idea of figuring out a way to still do this, but with a flat roof in the other portion of my house it makes it a little more complex trying to run a duct. 

[hpinson]

My older adobe house has all heating and cooling ductwork on the roof, and it is terribly innefficient in terms of energy loss, which is a shame considering how tight the house itself is.  We are looking into highly insulated and waterproof external ductwork, but have not been able to find anything like this available. That leaves us where we are now, with external ductwork wrapped in fiberglass with a coated plaster shell. which is terribly leaky in terms of both air and water (water damage periodically around exhaust ducts).  We have not been able to find a contractor with any ideas at all, and it is up to me to fix this now, hopefully next spring.  Would love to hear some suggestions to improve!

[NM_Shooter]

I thought too about putting a return duct on my roof.  But I'm not keen on the idea.

For a fix for your situation, maybe consider the foam roof solution.   They make do-it-yourself kits too, but it is nasty work.  I had a urethane foam room put down years ago, and I now have a small amount of ducting external on my roof that I have to fix due to a swamp cooler removal.  My plan is to insulate the heck out of the duct, frame it with wood, sheath it with OSB, and use urethane foam and acrylic to cover the whole thing.  When covered, it is bombproof with regards to water. 

The foam is a closed cell foam, so water does not penetrate.  The acrylic coat on top provides shade, since the foam itself is very susceptible to UV damage. 

My neighbor has had a problematic flat roof that has been leaking for 10 years in spite of two new roofs applied.  She now has urethane and loves it.  If you do a whole roof, make sure to coat up and over the parapets, or put metal rain caps over the parapets as water will follow the stucco down. 

[hpinson]

You are fortunate to have been able to minimize the roof ducting. We have many sends and a return.

When it comes time to re-roof- probably in a few years, that is the way I will likely go - urethane. I believe there are some other similar roofing products out there similar to Line-x (the truck bed protector) that I want to look into as well. Not a job I would want to do myself!

The complex way the pipe sends and return are arranged would make framing the pipeing difficult, but I wonder if the urethane could be direct sprayed onto the metal vent pipes?  I'm thinking yes, and that it also would behave as a good insulator.  I wonder what happens to urethane when it is heated-- does it off-gas? I will have to look into how inert it is once set.

One thing I am thinking about is getting rid of the roof venting completly and going to per room direct vent gas stoves. We have a soapstone Hearthstone Tuscon gas hearth in our bedroom, and we really like it.  Gives the apperance of a wood stove and it does a good job of warming the room. You give up some floor space, but I think it would be much more efficient given how tight the house itself is.  There is just so much heat loss as the warm air travels through the roof ducts.

[NM_Shooter]

Yes.... they spray directly onto galvanized metal, and it sticks pretty well.  I have a small amount of ductwork from an old swamp cooler, and the roofing guys sprayed right over that ducting.  It adds insulation and weather protection. 

It has some maintenance issues though.  I have developed some blisters in the foam (on osb) that are fairly large.  It also needs the hard acrylic coat re-applied every 7 or 10 years.  I'd like to find a way to do that myself, but have not found a solution yet. 

Mockingbirds will peck at the exposed foam if it is not acrylic covered.  I have some spots that have worn away, and they will get after it from time to time.  If I hear them, they usually never do it again 

[old_guy]

There was a post here some time ago where someone (Don_P, PEG, ??) mentioned running a duct from the far end of the house to the immediate vicinity of the stove.  The rising air at the stove pulls the air from the duct, or the stove heats it so it rises from the duct, or both.  This creates low pressure on the other (far) end of the duct, so the warm air near the stove drifts in that direction.

If you have a way to run the duct this might help.

Don't worry about throwing that heat outside.  I can use it here.

[Native_NM]

The lab we just tore down had extensive venting and HVAC.  The big ducts were galvanized and wrapped in 2" foam.  They used construction adhesive to attach.  They wrapped them in Tyvek. It held up for years. 

I've also seen the system used in Iraq - spray foams. 

[Native_NM]

I remember an episode of This Old House where they used micro ducts at high pressure to solve a similar problem.  It was an insulated flexible duct about 2" in diameter. Somewhere they had a fan which pumped the air.

[Bill Houghton]

NM Shooter, I have read a number of threads at Hearth.com (link below) about it being more efficient to move cool air into your wood stove room versus trying to move warm air out.  A search will bring up many threads over there:
http://www.hearth.com/talk/threads/moving-heat-to-other-rooms.93528/#post-1259829

[MountainDon]

Interesting. But you would think that moving warm air would work too as if air is moved from A to B in a duct it must also flow by itself. I'm thinking of all the homes around me that are built with a hot air duct from furnace to each room (with ducts in ceiling or a conditioned space above the ceiling). No cold air returns from each room; just a big intake at the furnace. Same ducting used for cooling.