View Full Version : new heating system
09-14-2005, 12:13 PM
Im looking for input on the type of heating system im looking at for new construction in New Hampshire. I have had two heat load calucations done which range from 67 to 82KBtu heating and 26 to 42 KBtu cooling.
First system was a geothermal heat pump using radiant throughout the house, a second air system throughout the house with electric backup. The radiant provides 57 Kbtu heating with the air system providing another 50 KBtu as a primary backup. Hihger install cost but possible lower operating cost.
The second system consists of a two zoned FHA by propane with one unit located in the attic and one in the basement. I am requiring radiant heating in at least the tiled areas of the house (kitchen and bathrooms). This company recommends a serperate on demand water heater for the radiant portion. The cost just of the FHA portion was almost half of the GHP system.
I am trying to find information on Hydro-air furnaces but cant seem to find a manufacturers.
09-14-2005, 12:59 PM
Propane is the highest cost of heat. The geo radiant/forced air cooling route would be the cheapest heat and most comfort.
Hydro air units are simple blower coil units. The heat is supplied by a boiler heating water that circulates through the coil. Going this route with an oil boiler could be a lower first cost and an economical annual heating bill.
If it's new construction, you can adjust your budgets to spend a lot more on the house envelope and reduce the cost (and operating cost) of the HVAC system. The total cost of the house will be the same in the end, but you can reduce the heating and cooling loads to a very low value with high performance windows, properly designed exterior shading, minimize thermal bridging and appropriate insulation, and you can do the whole house with radiant and a small ERV/HRV and have much better comfort and much lower energy bills. Nice combination with a smaller geothermal system.
It's all about the process and control thereof.
09-14-2005, 02:56 PM
Whole house radiant?
What is your take on radiant under the subfloor (between joist) and carpet with pad for floor covering?
We are building to an HERS rating of 89 to improve the efficiency.
09-14-2005, 02:59 PM
Originally posted by ktm250rider
I have had two heat load calucations done which range from 67 to 82KBtu heating and 26 to 42 KBtu cooling.From two tons to 3.5 tons for cooling? Why is there such a wide variation in load estimates?
09-14-2005, 03:05 PM
I had two different calculations done. One was for a heat pump supplier and one was from our public service company. Just to clarify
Heat loss 82 KBtu per hour
Heat gain 42 KBtu per hour
Heating load 67 KBtu per hour
Cooling load 26 KBtu per hour
09-14-2005, 03:09 PM
I'm curious as to what information the supplier used to perform the load calc?
Cause something is seriously wrong here!
09-14-2005, 03:09 PM
Something is wrong with one or more of those heat gain calcuations. The variance shouldn't be that much.
Trying to do radiant by putting the heating element under some insulators (subfloor, underlay, carpet) is NOT an efficient way to do it. The closer the heating tubing is to the heated surface, the lower the temperatures you have to use, and lower energy requirements. Seriously look at some kind of Warmboard panel (Rau Panel etc.) on top of the floor. Ideally the radiant should be in a lightweight concrete topping for best performance (energy and comfort). If carpet is being used (another insulator on top of the radiant surface) then at least use some high density underlay to help transfer the heat from the floor to the carpet. An astute heating system designer can also look at the economy of installing the radiant in the ceiling and on some walls, and avoid the masking and insulation by furniture and carpet.
09-14-2005, 03:28 PM
The lower of the two was done with my house plans with window data, insulation data etc using Home Energy Ratings System software. Im not positive how the higher report was completed.
Ive also heard radiant under carpet is not a wise choice. Thats why Im just doing it under the tile and garage.
09-14-2005, 03:44 PM
Originally posted by ktm250rider
The lower of the two was done with my house plans with window data, insulation data etc using Home Energy Ratings System software. That is most likely the correct one, then.
09-14-2005, 03:55 PM
The other one was likely figured off of SqFt, which is why the figure is higher.
09-14-2005, 03:58 PM
I believe it was sqft based on simplified construction detail.
09-14-2005, 04:15 PM
The 'tons per square foot rule' contractor is either lazy, poorly trained, or a hack.
09-14-2005, 07:41 PM
Find a solution between GSHP and FHA. Radiant requires a boiler, so why bother with FHA? Radiant floors in bath and kitchen with panel rads for the rest of the house makes for one nice hydronic mix. Get an indirect HW heater and everything is running off one burner, very efficent and confortable with as many zones as you'd like. Oil is usually a cheaper solution in the North East.
Take a look at this design, handles multi temp zone requirements very well:
In NH, I would concentrate on getting the best heating system for your money. You're AC needs are secondary and could be handled by a small split system or mini-split units for the few weeks you need AC.
[Edited by johnsp on 09-14-2005 at 09:41 PM]
09-14-2005, 08:34 PM
John's plan is the best. There just isn't much cooling load, there. Focus on being comfortable the 10 months of heating season. I can't imagine having air blowing on me when it's below zero out.
I have a house that I built in Sutton. I speak from fuel buying experience. So does John, I see.
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