OK, I have to apologize on this one. You are right. It goes down to a super low fan speed when the compressor shuts off in heating mode,

I like having that cool air blow on me in the summer and most people do that live here in Crematoria(Texas). So weather it’s the vent itself or the fan it’s a moot point. And in the winter how many people don’t often scout out that spot where they can stand and have that hot air blowing on them.

Now when it comes to running your ac in reverse to heat your house we all know the temps are typically not as hot as a proper furnace and having that cooler air blow directly on people is not a good idea.

My issue with heat pumps is that like others have mentioned they are often not any cheaper to run than a gas furnace. The only way I can see a heat pump as being a great choice is if you also produce your own electricity barring that it’s case dependent. We are talking central air systems as those are the standard in N america. Their efficiency is really pretty poor for units that the average homeowner can afford. If you are in a cold climate or anywhere that has cold snaps I would NOT rely on a heat pump as my only source of heat. And never rely on one heating or cooling system for your house. Always have a backup for at least an area of your house.

But the memory of heat pumps from the recent past has still put a large number of people against them. For many years they were difficult to install, high failure rate, not really cost efficient, couldn’t heat much below 40* and they had heat at the vents that was hard to tell if it was working. That is not the case anymore other than I’m not impressed with typical split system efficency still.

Then when you bring in the minisplit systems which are not well received in the US as most don’t want that big thing hanging on the wall. Those will always blow on people. Just how it is with the typical ones and most people aren’t going to complain about them because their vent temps are pretty high and low for cooling.

I’m watching what’s going on over in England with their push for heat pumps and loads of problems there which start with their overcomplicated hot water radiator systems. Lots of unhappy and cold people there.

And the other heat pumps out there like PTACs and package units they really don’t make sense. I’d really like to see allot more insulation and a decent bump in efficency of package units as they have allot of good uses since it’s all outside in one box and easy to swap out. Not hard to do but they would be physically larger.

Step one is for a proper Manual J to be completed. I would suggest attempting to do one yourself if you feel up to it. Google for CoolCalc. It is involved but one can learn how to do a credible Manual J with CoolCalc. The value of doing one yourself is that you have something to compare with the HVAC contractor. If yours agrees then step one is hopefully good. If it disagrees enough to affect equipment sizing then you need to have a discussion with the HVAC contractor or builder. They may or may not be open to that discussion. Manual D duct design is pretty complicated for most people and unfortunately even for many HVAC contractors. These days an HVAC contractor should be using WrightSoft or similar software for their Manuals J, S and D and be willing to share the reports with you. ACCA publishes some checklists for building inspectors that homeowners could use just as well to do a reasonability check on the HVAC contractor’s plans. You can also ask them the design total CFM per unit and crosscheck duct capacity against their plans, possibly with a ductulator. Its a huge red flag if the HVAC contractor is not using approved design software for both the Manual J and D and further indicates using “proprietary methods” or “rules of thumb”.

The reason to doublecheck the HVAC contractor is simple. Too many still use the old rules of thumb methods. HVAC system design is very complicated and many companies avoid utilizing the available software design tools and requisite training. I have experience in this area so I double checked my builder’s HVAC contractor and found their design to be massively wrong. The short story is that the furnace was sized at 80k btuh when only a 60k btuh unit was required and the ductwork was undersized even for the correct furnace let alone the oversized one. They did not follow manufacturer instructions properly for installation of the furnace, humidifier or media filter. On top of it all, the furnace high limit tripped constantly due to all the design deficiencies and NOBODY noticed that because they clearly failed to run anything even vaguely resembling a commissioning process. After numerous significant discussions with the build I at least got the furnace replaced with the proper size under warranty. I am dealing with the remaining duct issues myself.

You are paying for a new house with a new HVAC system. You should get what you are paying for with a properly designed and functioning HVAC system.

UnfortunTely Allison, you are mistaken on the Mitsubishi Mini Split sequence of operation.
Some heat pumps work with a constant speed compressor, but the Mitsubishi systems use an inverter operated variable speed compressor that is intended to modulate the compressor to maintain constant operation at a lower level, which actually will blow warm air constantly. When properly sized It will in fact operate past the control setpoint before it will shut off. This results in a system that will vary the discharge air temperature in relation to the difference between room air temperature and setpoint. In colder outside temperatures, it is not unusual to see supply air temperatures above 110 Deg.F. which is close to a high efficiency gas furnace.

Hello Allison, Thanks for the educational article. I had thought that it was common knowledge that air to air heat pumps deliver colder air than furnaces and that one must compensate with larger volumes. However, I can’t help but see this as a bug and not a feature, making these devices less appropriate for retrofits to existing ductwork. To be pejorative, I don’t think that blowing larger volumes of cold air around a building sounds very comfortable. 😉 I suppose it must be an HVAC installers nightmare, and not anything I want to grapple with so I stay away from it my work.

As a young man entering the renewable energy field 40 years ago, I had my nose, (necessarily) rubbed in energy and environmental economics which is something that I now much plague my colleagues with, so my apologies.
In my area heat pumps are just barely competitive with condensing propane appliances or and ~15% more competitive with fuel oil with respect to “fuel” costs, but not enough to produce a payback on the increased investment. For condensing natural gas fired appliances produce heat at 3x – 4x the cost of operating electric heat pumps so there is a negative payback on the heat pump making it an expense rather than an investment.
I try to maintain some professional ethics around what I do and I can’t in my right conscience sell a homeowner on and expensive retrofit that not only shows a negative payback but I know is environmentally irresponsible as well.

I am very happy to report that when I come into the house on a very cold day, or if I’m just chilly for some reason, I can stand over a floor diffuser and DEFINITELY feel very warm air that instantly takes the chill off. I can hang towels over a floor diffuser and they get noticeably warm.

My ducted mini split fan quietly runs 24/7/365, makes the house very comfortable and definitely puts out air warm enough to notice the difference between the room temp air, in a very very nice way!

Mike: Yeah, if you have a right-sized furnace with right-sized ducts (uncommon) or an oversized furnace with undersized ducts (most houses), doubling the air flow rate means the existing ducts may not be suitable. But doing some retrofit work to lower the loads can reduce the system size needed and thus the required air flow.

Ed: Good points. I haven’t yet written about the what happens to utility costs when you switch fuels, but it’s on my list to cover soon. In some cases, it’s a no-brainer to switch to a heat pump because the savings start immediately. I’m thinking of homeowners who currently heat with oil or propane. In others, going to a heat pump can increase utility costs. And in some cases it can add a lot. That would be true for an area with low gas costs, moderate to high electricity costs, and a heat pump that uses too much strip heat.