I am searching for a builder for a new home and have found something I have never seen before – the furnace and heat exchanger in the attic. Several of the builders in my area (SE Washington) are using this technique. The capacity of the system is the same as would be installed in a first floor location of a two story house. It seems dumb to me, but all the builders say they have experienced no problems. I haven’t had the courage to challenge any of them directly by pointing out none of their houses are yet old enough to have experienced a breakdown in the HVAC system.
These builders have good reputations and can build the size house I want within my budget. Any opinions on these systems?
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The house we are renovating at the moment has two furnaces, one in the basement and the other in the third floor attic. They are both the super high efficiency types that require only 3" PVC for exhaust, and the attic furnace vents out the side of the dormer. This was done because the house had been divided into an up-down duplex, but we are returning it too single family. I haven't noticed much difference between the two systems, in that the upper unit blows down from vents in the ceiling and the basement unit blows up through floor vents. I have noticed that the air return for ours is a bit screwey as it is located at the top of the third floor steps. When we first used it, warm air would come from the vents, zip across the ceiling, and then shoot through the doorwell on the stairs and up to the return. The third floor just cooked. I installed a door in that opening, and near the bottom put a couple of large air return vents which were equal to the size of the air return duct. That really helped to even out the heat on the second floor and also make the third floor bearable. I mention this only so you pay attention to how the air is circulated in the house. Make sure the air return is located low or you may find yourself just re-heating the warm air.
It's very important to properly seal the ductwork: loose distribution plenums and you're pressurizing the attic and losing heat; loose returns and you're depressurizing it and circulating all of that nice attic dust through the house, etc.
In my area, the use of attic furnaces hasn't been around long enough to know if it'll affect the life of the furnace or it's components.
If you do, make it really easy for the service people to get to it and to work on it. Common sense. Make it a pain in the azz and how good a job will they or can they do? (And how good will the initial installation itself be?)
In my area most new constrcution with attic furnaces "violates" that common sense rule: they squeeze 'em in between the trusses with minimal and awkward flooring. I've seen several where it was a major pain just to change the filter!
Bob
The Building Science people really push moving the insulation to the roof and so that the furnace and duct work are in conditioned space.
They claim that it was a big difference in AC in the SW.
Bill,
Thanks; good to know.
Them's regular building practices here in Texas. Our house is only 18 years old and still has the furnace inside the house. I don't know when this practice became the norm, but it was some time within the last 15 years or so, I guess. Every time we got thru the 'parade of homes' in the neighborhoods, they are all in the attics. Go figure.
I don't think it is anything new. An Air Force housing development in GA had them in the mid 60s. I've run into a number here in CO. Also seems they were common in the Dayton OH area. Carrier has listed them in catalogs at least since 63. Biggest problem as already been alluded to: maintenance and filters can be a bitch. Noise can also be a problem if not properly installed and as has already been mentioned duct and plenum leakage, althought that is no worse than many floor mounted units with attic ducts. Advantage is no loss of floor space.
I have a 44 year old house here in California with the furnace in the attic. No problems and it is the original natural gas furnace. It is common practice here. Noise and proper venting are important as is maintenance access.
If you go with a furnace in the attic, not a bad idea if properly carried out, the installer should put in a GFI protected outlet and a light near the unit. Seeing as that anyone who works on the unit, repair or maintenance, will be charging you by the hour these additions will save you money in the long run even if you have to pay extra. Some areas mandate these be installed per code but other areas don't enforce the rules.
Another thing to add would be a 2' by 4' piece of 5/8" ply placed in front of the service panel of the furnace and cleated with 1 by 2s screwed to the bottom to prevent the sheet from sliding and gives a technician somewhere to lay or sit when servicing the unit. A set of cleats on either side of the ceiling joist holds the ply in place while allowing the ply to be removed to route cables or pipes.
For real attic luxury throw scrap 5/8" ply ripped to 12" across the ceiling joists for the length of the attic. Anything along these lines makes maintenance faster and easier and saves you money. If you do your own maintenance you with thank yourself every time you use these features.
I have picked up a small elec. furnace that I am going to mount in the attic of my garage/workshop.
If any of you do this, I suggest:
- Putting pre-filters on your air intake vents where they're easy to access.
- Put the furnace in an insulated enclosed area, per manufacturer's specs. so it's more efficient.
- Definately wire in the light & outlet as suggested.
- Definately provide a place to stand or sit and work on the furnace.
- Most importantly, put a hard wired smoke detector in the attic, preferably one that will set off other detectors so you'll hear it. An attic fire is as bad as it gets, w/o a detector you may not realize there's a fire until the ceiling falls in.
- Whatever you do, make sure you do it safely.
Just my thoughts
BillG
Rule of thumb: Heat is better distributed from the floor since heat rises and air conditioning is better distributed from the ceiling since cool air settles. Ideally we would have to separate air handling systems, but the cost would be prohibitive. You will find that HVAC is in the attic more in the warm climate areas and in the basement more in the cold climate areas. I would not think that you would use too much AC in Washington state, so I would opt for a basement system.
I intend to distribute the heat near the floor. by the workbench.
Going to run ducting down the walls behind some shelves.
The cold air return will be near the other end of the garage.
Just where I have space for a furnace.
Thanks for the input.