Resources to Share With City Officials
I am doing a deep energy retrofit on a house built in 1870 in Chicago. I have spec’ed it to utilize only a multi-zone heat pump for heating and cooling which, given the air sealing and R-44 walls, R-70 roof, and R-20 basement walls I believe I should be well past what code dictates.
Building plan review here is pretty backed up and I want to ensure a minimum of rework if the city comes back with comments. My architect was pretty unfamiliar with heat pumps but spec’ed it as I requested. My GC is insisting that the city will outright reject the plans without at least radiant baseboard heat as a back up.
In case the city comes back with requesting those changes I want to be prepared – are there any resources I can use for these types of discussions with city officials?
GBA Detail Library
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Replies
There is nothing in the code that prohibits heat pumps as the sole means of heating. Period. Capacity should be the only item of concern and that is addressed with load calcs and the specifications of the unit you want installed.
If I've learned one thing with code officials its to never ask them permission if the permission isn't theirs to grant. Tell them what you're doing and why, and if they push back request the code language justification. Most of them are reasonable but if you ask "can I" and they're unfamiliar with what you're doing then "no" is the most expedient answer.
Jason,
I'm sure you are right, but this "requirement" seems to come up here quite often without anyone being able to say what is behind it. Does anyone one here have any insights? Does it come from heat pump's low temperature performance?
Yes, basically you can search the topic and several threads lead me to believe that people just installed baseboard heaters to appease inspectors. Chicago has a reputation for difficult inspections so I'm just trying to get my ducks in a row.
I think it's out of concern that a heat pump might have issues in low temperatures, and that the building dept people just don't see enough of them.
The simplest solution is to just install a cheap electric resistance heater as a backup, then don't run it. This will make the building people happy, it won't cost a lot, and you know you won't really need it -- although it IS nice to have a backup. Regular furnaces can quit too. I've seen control board failures, inducer motor failurs, just about anything can break. On of the pluses of having two zones with seperate furnaces is that if one fails, you can still run the other one while you're working on repairing the first one. Partial heat is better than no heat.
Bill
See Dana Dorsett's response #3 here:
https://www.greenbuildingadvisor.com/question/is-there-any-way-around-putting-a-heat-source-in-every-bedroom
The code section in 2021 IRC is now R303.10 but it reads the same. You need a heat load calc and unit specs to prove that it can meet it.
If I had to hazard a guess as to all the fuss someone in the Chicago building dept went to some seminar sponsored by Trane Carrier Rheem etc etc...
I'm going to take this advice (along with a printed copy of your code below) and hope for the best. I'll report back if there are issues along the way.
Did you size it according to Manual J? Does the published output of the heat pump at your design temperature meet or exceed the heating requirement in your Manual J? Then it meets IRC. Chicago may have code amendments that say otherwise.
Multi zone meaning ducted or ductless? Having rooms without their own heat sources might be what your GC is referencing.
Edit: saw that the GC said you need radiant baseboard heat as backup. Ha!!! Not a chance.
All rooms will have a ductless head.
There's no way to fit ducts? Seems like you'll have an underperforming heat pump with those levels of insulation
Why would this underperform? Ducting could be fit but one of the reasons to do this is to gain ceiling space and save money on foregoing duct installation. I was under the impression that ductless was more efficient.
It's not ducted vs. ductless necessarily, it's situational. If you have a multi-zone ductless installation with a ductless head in each space, especially with your levels of insulation, your system will short cycle. A short cycling system will not perform well, ductless or ducted. A ducted system can very well short cycle, but it's less likely. It's likely now that you have rooms with ductless heads that have worst case heat losses below their minimum modulation.
What's the total number of ductless heads? And what's the building's heat loss?
It's discussed well here:
https://www.greenbuildingadvisor.com/article/multi-zone-heat-pump-issue
My local inspector had issue with my heat pump as the sole means of heating the house. After further research and thoughts about zoning, I decided to go with two outdoor units (2 separate systems) and this was enough for them to leave me alone at the same time.
It seems likely given your level of insulation it seem impossible that you will be able to find head units small enough not to overpower each room. When we see the head in every room designs the systems always seem to be hugely oversized with several heads on each outdoor unit this make matters worse in that multi head unit can’t run as slowly as single units. Also the head in every room plan tends to fail when the bids come back at 50% more than a conventional HP system.
I think your GC may be correct in that they are likely to reject any plan without a heat source in each room. It seems adding a few low cost electric heaters will make them happy even if you never turn them on.
Walta
Walta is absolutely right - heads in every room will be inefficient and uncomfortable. Even 1 outdoor unit per 1 indoor unit with incredible modulation might struggle with these low load rooms. If you do 3-8 indoor units per outdoor unit, it’ll be even worse.