Hi, I recently was asked by a heating contr. what is a cost-effective & durable method for installing a section of heat ducting underground, from the main house to another heated structure. The length of run would be approx 130′.
Oregons’ Code is VERY limited on specifics…basically requring it to be encased in concrete! Worth noting, the house will be heated by a boiler heating system..main structure is apprx.4000 sq. ft.
Any help would be appricated.
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Replies
Pipe over hot water; or install a heat pump in OR.
130 ft of 'hot air' ducting is 'strupid', unless you cantap into the city council chambers for a source.
Your heating contractor (this for yur house or just a hvac guy asked you) is unimaginative.
You would prolly geyt some good alternativres over at "breaktime classis", most knowledgeable folks moved there.
the house will be heated by a boiler heating system
And that system would be?
If radiant hydronic you could probably run a full temp line to the other place, to a manifold and distribute from there. How much heat loss would be the deciding factor on whether if wouldn't make more sense to install another boiler or even water heater to do the job. You don't want the return water to be too much of a difference coming back to the boiler. I suppose you could retemper it at the house prior to the boiler.
If the boiler is being used for the forced air heat source and you don't want to have radiant over there, I still think you'd be better off with a different heat set up in the outbuilding.
What would that outbuilding be anyway?
Is this the best your heating contractor could come up with? or are there other alternatives?
I guess he wouldn't be over at Breaktime Classic in that case..............
This is not for my house. It is for someone else. I am just trying to answer some questions the heating contr. has. He has not experienced doing this type of ducting, either.
As for the boiler heating system...I only know thats what the contr. has stated it would be.
The other building I believe is for a guest house.
I believe there must be other systems out there, but for whatever reason the client seems convinced this is the "way" to heat the buildings...it must be some "green" or "carbon-neutral" thing...Oregon is starting to really get into this "save the world" thing.
I won't go into my belief into that, though!
Thanks.
If you're starting with hot water it's foolish to heat air and then pump the air a long distance. Hot water can much more easily be installed, it's easier to insulate, and it takes less energy to move a given amount of heat from point A to point B.
If hot water isn't the answer for whatever reason, either a small high-efficiency gas furnace or a geothermal heat pump would be the way to go, for "green" purposes.
Hot air, pumped that distance undergound, is the least "green" of the alternatives.
Encase about a 6" piece
Encase about a 6" piece (maybe larger) of conduit in concrete and then fish PEX through that. Maybe you can find some PEX that's insulated with a fairly compact insulation layer.
Thanks, but the contr. said he is looking to run about a 12" spiral in the ditch!
I really believe this whole way of heating via underground ducting is not efficient nor cost-effective. The contr. is already at about 50,000 just for the material! (I believe i am in the wrong business).
I will talk to him later this week to see why this is really needed to be ran undergrnd.
Crazy!
The only place I have seen underground ducts was in a toll booth (MM99 I-75 Fla)
They do it so they can pull fresh air from behind the admin building instead of the exhaust laden air on the road.
It is a 100% fresh air makeup system.
The duct was run through a formed concrete tunnel and tapped off at each booth.
Yeah, it's not that unusual to run ductwork in large buildings through ducts of that sort. (And, of course, we have below-slab ducts in our basement.)
An underground forced air duct
from one building to another, in the situation I think you're describing with a guest house and a main house is THE LAST THING I WOULD EVER DO! The heat loss in such a situation would be very significant, the chances of problems and/or failure are high, and the alternatives are many. Oh, and are you going to run a return air duct also? All the trenching, the concrete, the cost of SpunStrand or another below-grade ductwork material... this is so NOT green it isn't funny.
Why not install a ductless heat pump in the guest house, or some other small, efficient unit? There are plenty of options. You need an HVAC contractor who knows what they're doing.
/rant
Thanks so much for all the input!
I agree with everyone here that this method is not "green" nor efficient. I am not sure where this homeowner got the idea of it being so.
There are very efficient split/ductless systems out there, as you obviously know.
Thanks again for your input!
for whatever reason the client seems convinced this is the "way" to heat the buildings
Ignroance, true disciple of algore, or ??????
With the expenditures (50K!!) mentioned, I'd say the hvac contractor has a hot bite and a live one on the line!!
If the HO can pay cash, suck it up and spread the wealth as most in OR would like to do <G>
, if someone on a tight budget, print this thread for the HO......
..course, with a name like 'junkhound', wtf do i know?? <! :)>
Thanks.
I understand $ is not an issue, though I've been told that by several people over the yrs when they have these pie in the sky dream houses, soon though, they quickly find that there is a bottom & in some cases they've been fleeced...unless you are the government...the only people who are fleeced are the taxpayers!
For $50,000, he can knock down his existing guest house and rebuild it super-insulated and heat it with a hair dryer.
In commercial construction this is often done. I think they use Spun Stran (brand?) duct. A fiberglass duct specifically designed for this. We used in up in the Spokane are quite a lot. Not sure about the insulation aspect of that approach ... but if you find the product, I'm guessing you'll easily find someone that knows about that as well.
Otherwise, the other posters are right ... water is better transported 100 ft than air. But only you/your client know if that is out of the question or not.
Correction, that is Spunstrand ... a brand name that has been around for a long time. http://www.spunstrand.com/
I googled it ... check it out, might be the ticket if that is the way you have to go. Again, not sure about insulating, but a call to their rep will answer that I bet.