Natural Gas Furnace vs. DFS Heat Pump
I am remodeling space above an unheated garage that will be used as a guest bedroom w/bath and an exercise room. My house currently has natural gas forced air furnace, but given the location of the remodeled area, I will need to add a new heating/cooling source. I am considering either adding a small second forced air furnace with AC or a duct free split heat pump.
Key considerations include:
– I am located in the Syracuse, NY area, where we get a lot of snow and cold weather
– the exercise room would only be used 4-5 time per week (hopefully!), and the bedroom only occasionally, so I’m looking to be able to heat/cool the space quickly, and when not in use, adjust the temperature accordingly to save energy.
– I am mostly concerned about the ongoing operating costs and the comfort level, and not so much about initial installation costs. And the ability to adequately heat is much more important than cooling (heat is a necessity, cooling is more of a nice to have)
The DFS heat pump seems to be a good option, but I’m not sure of how efficient it is at quickly heating a space, as well as how well it would operate in sub-zero temperatures. I know there are some newer units that claim to operate in extreme temperatures.
Any thoughts on these options is appreciated!
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
Mark,
I'll give your post a bump. Your space might be a good fit for a hyper-heat-type split system. How large is the area? Also... How do you intend to insulate the roof line, what steps are you talking to keep conditioned air from infiltrating into wall and roof cavities?
The heat pump option also allows you to cool & dehumidify the space in summer, which can be pretty important for an exercise room.
Run a heat load calculation on the space to estimate the sizing. Loadcalc.net or Coolcalc.com Manual-J(ish) load calculations will be good enough if you're agressive on the input assumptions. Assume the place is 100% air tight and unventilated (even though it's not) or your oversize factor will get out of hand upsizing from there. Those tools regularly overshoot reality by 25% or more even with aggressive inputs.
The 99% outside design temp in Syracuse is +3F (yes, I know it gets colder than that), and if heating up quickly is important it's reasonable to oversize the equipment by 1.5-2x the design load. M ore than that becomes noticeably less comfortable when actually using the space, and efficiency starts to suffer at 1.5x oversizing, potentially an efficiency disaster at 3x oversizing.
The searchable NEEP data base covers many Carrier/Midea models, and lists the max capacity @ +5F, which is close enough to your design temp to just go from there.
https://ashp.neep.org/#!/
With load numbers it'll be easier to make specific model recommendations.