It’s coming, and I will simply say we can do this. Electrification is not going to be easy, though. I think it sings an opportunity for better contractors and puts another nail in the coffin of those contractors who design and install systems that are less than ideal.
I have experience in a cold climate, you can heat a space and make it comfortable with a heat pump, but everything must be done properly. Not just the HVAC, but the house too. Fuel-fired heating is much more forgiving.
I have lived in homes with heat pumps for the last 30 years. I know how they condition a home. I use fuel-fired radiant heat on all the hard surfaces, and I love the way it heats my home (I’m telling you what kind of heating system I have to be fully transparent). Everything I speak about comes from practical experience that I have obtained over the last 30 years or so.
Major Concerns About Electrification:
Is the Housing Stock Ready for Heat Pumps?
- Good shell
- Adequate insulation
- Supply outlets
Homeowners don’t like to spend money on home performance. It’s been my observation that people aren’t interested even when it’s deeply discounted or almost free. There are people that pursue it, sure, but it’s far from mainstream. A home with a good shell is reasonably tight, X ACH50, or less. Adequate ventilation takes care of indoor pollutants such as CO2 and VOCs. You need enough fresh air so that when it is added to the infiltration that occurs naturally, it equals the amount specified in ASHRAE 62.2. Adequate insulation varies from place to place because of the differences in climate. Required amounts should be based on your state’s version of the residential building code. I would guess that every house built since 2000 is code compliant has adequate insulation. Anything older than that would typically benefit from additional insulation.
Supply registers matter! Don’t blow air on people! Expect comfort complaints if the supply registers are in bad locations. Furnaces let us “get away with that,” those high supply air temperatures made the air feel good. Heat pumps have much lower supply air temperatures and if they “blow on people,” they will complain.
Duct Systems & Humidity
- Poor latent capacity
Most existing homes have duct systems that are in attics or crawlspaces that are too leaky. That’s a big issue. I’m all for right-sized equipment. But leaky houses with leaky ducts and a right-sized heat pump will work like a $2 watch…not very well. HVAC professionals must put fixing leaky ducts on every heat pump quote.
Next on the bad list is duct sizing, as most duct systems are undersized. But, even if the ducts are sized properly (and tight) for the current air conditioner/furnace, when we select the heat pump to meet the load, we generally need a larger heat pump and more airflow. We’re back to the problem of undersized ducts again.
We must sharpen our pencils when it comes to our equipment selection. In many climates, the larger heat pumps that are required for heating can create a real issue if the summer latent load isn’t addressed properly during the design process. Don’t automatically assume that two-stage or variable-capacity systems will automatically do a proper job of moisture removal. It must be proven by the OEM expanded performance data.
Is this the end of the world? No, but it’s something we need to pay attention to. I think resistance to upgrading duct systems is the norm, as people are more interested in switching boxes. Air conditioners are tolerant to low airflow, but heat pumps are not. There are many systems that currently work well that will need modified ducts when we electrify with heat pumps.
NOTE: Adequate electrical service: This one isn’t as big a deal as it could be, but it’s something that needs to be paid attention to, nonetheless. Air handlers typically need a 240v circuit.
Manage the consumer’s expectations: Not to sound like a broken record but installing a heat pump in a leaky house with undersized leaky ducts is a recipe for disaster.
You must prepare to fend off these potential problems. They require proper design, installation, communication, and home performance preparation to deliver predictable comfort. I am perpetually a glass is half full kind of person, but I see lots of callbacks, complaints, and bad reviews for contractors who don’t do this right.
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Posted In: ACCA Now, Electrical, Residential, Technical Tips
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