Heating Options for New Addition?


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Old 07-08-11, 06:14 AM
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Heating Options for New Addition?

I posted a similar query in the Heat Pump section. Now, I'm not sure, given my options, what would be the best alternative.

I currently live in the Northeast and my home is an executive style, U-shaped ranch with approximately 3K sq. ft. of living space with another 700 sq. ft. partially finished basement. My current heating system is a 10 yo, oil burning, hot air system. I also have central AC (one 4 ton compressor?). The house was a contract build and built in 1980.

I'm in the process of having a 500 sq. ft. great room addition built with a basement and I'm considering my heat/AC options. I was told by my HVAC contractor (and oil supplier) that my current systems wouldn't handle the additional square footage and that I'd need a second oil burner and a second 2 ton AC compressor with duct work. I was quoted approx $9K for this work. Given that I intend to install a 40K btu propane fireplace in the new room, this sounds like overkill to me, not to mention a little on the high side.

While my current system seems to operate fine, I don't believe it's very efficient given that I spend more on oil than the average despite maintaining reasonable temperatures (62-68 degrees winter).

The contractor building the addition suggested I wait to see how the current system handles the additional space which seems reasonable.

Would it make more sense to add say a ducted mini split/heat pump? Would it be possible to upgrade my current heating system to something more efficient/greater size to accomodate the additional space? Other thoughts?

Thanks in advance-

BTW - here's info on my current furnace:

Lennox Elite
Model C23-51-1
AFUE 81.0
Least effective AFUE 78.0
Most effective AFUE 86.7
 

Last edited by neskier; 07-08-11 at 08:44 AM.
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Old 07-08-11, 07:42 AM
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Houses of that era were generally built with less insulation and less care concerning air sealing so there is usually a lot of room for energy savings improvements on the house envelope. Add to that the fact that heating systems were also oversized as a general rule and that means that it is definitely possible that you can extend your present system to handle the new addition IF the arrangement of the new space to the existing furnace is conducive.

However, if you are still using the original furnace then it is definitely time to investigate new equipment. The VERY FIRST thing you need to do (or have done) is a complete "Manual J" heat loss / heat gain analysis and then factor in any energy saving retro-fixes that are reasonable.
 
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Old 07-08-11, 08:02 AM
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I agree with Furd but would go one step further. Instead of just the manual J, I would opt for a full energy audit, especially while the new construction is in progress. Improvements that are being recommended from today's energy audits will certainly help you reduce the load on that current system and I suspect easily handle your addition. Even if a new system is a consideration, you would want the reduced size, cost, and yearly savings that come with energy improvements. Adding another furnace or system would increase your already high energy bills and be a step in the wrong direction.

Bud
 
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Old 07-08-11, 08:04 AM
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It is actually the second furnace installed approximately 10 years ago. There are currently three ducts/registers supplying what will be the entrance to the new room (possibly extend these?).


Originally Posted by Furd
Houses of that era were generally built with less insulation and less care concerning air sealing so there is usually a lot of room for energy savings improvements on the house envelope. Add to that the fact that heating systems were also oversized as a general rule and that means that it is definitely possible that you can extend your present system to handle the new addition IF the arrangement of the new space to the existing furnace is conducive.

However, if you are still using the original furnace then it is definitely time to investigate new equipment. The VERY FIRST thing you need to do (or have done) is a complete "Manual J" heat loss / heat gain analysis and then factor in any energy saving retro-fixes that are reasonable.
 
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Old 07-08-11, 10:24 PM
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Again, and also as Bud wrote, you cannot do this on a guess. You NEED an assessment of the actual heating/cooling needs of the entire house and the additional needs of the addition. There is no "rule of thumb" that is going to give you a definitive answer.

Your present furnace MAY be adequate for heating and the present ducts MAY be such that they can be extended but you can't KNOW this without the proper calculations. Even if the heating power of the present furnace is adequate it is possible that the cooling system would be INadequate.

If you want to do the calculation yourself the following program has been recommended several times over the years. It is a bit pricey to purchase but you CAN get limited usage for a single home for $50. It may well be the best $50 you will spend on your project.

http://hvaccalc.com/main.asp
 
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Old 07-09-11, 05:54 AM
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Question for you. On your hottest and coldest day, does the system run non-stop or does it cycle on and off? If it cycles, chances are it may be oversized.

Also, Who ever told you need 2 ton in 500 sq ft area is out of their mind!
 
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Old 07-09-11, 09:46 AM
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It cycles on and off. The contractor asked me the same question and indicated the same thing.

An HVAC guy indicated that a 1 ton wouldn't quite do it and a 1 1/2 ton (?) unit isn't available.


Originally Posted by Jay11J
Question for you. On your hottest and coldest day, does the system run non-stop or does it cycle on and off? If it cycles, chances are it may be oversized.

Also, Who ever told you need 2 ton in 500 sq ft area is out of their mind!
 
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Old 07-09-11, 10:53 AM
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If none of your contractors have done a manual J or the parallel approach of an energy audit, then everyone is guessing. Your new addition should be as tight as possible and extremely well insulated. It's heating and cooling loads should be minimal. If your furnace is cycling on very cold days, then it is not at its max. A little attention to duct sealing and weatherizing the existing home and after adding on the new, your old furnace will still have capacity, but do the J.

As for the old "bigger is better" approach for the ac, you don't want an oversized system that will cool in short bursts and leave the humidity behind. Smaller systems run longer and remove more moisture.

Good luck
Bud
 
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Old 07-11-11, 10:23 AM
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Originally Posted by Bud9051
If none of your contractors have done a manual J or the parallel approach of an energy audit
Should any HVAC contractor be able to do this?
 
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Old 07-11-11, 09:18 PM
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Originally Posted by neskier
Should any HVAC contractor be able to do this?
the Manual-J? Yes. Energy Audit, No. it's offered by most utility company.. My gas company offer it.
 
 

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