Author Topic: Heat pumps on the rise after Minnesota passes new energy law  (Read 7588 times)

rcjordan

  • I'm consulting the authorities on the subject
  • Global Moderator
  • Hero Member
  • *****
  • Posts: 12952
  • Debbie says...
    • View Profile
Gonna be a cold winter in Minnesota unless they have auxiliary heat strips and $$$ if they do.

https://techxplore.com/news/2021-07-minnesota-energy-law.html

Brad

  • Inner Core
  • Hero Member
  • *
  • Posts: 3501
  • What, me worry?
    • View Profile
Re: Heat pumps on the rise after Minnesota passes new energy law
« Reply #1 on: July 10, 2021, 01:30:08 PM »
A lot of people in Minn. , especially rural, have wood burners or pellet stoves as supplemental/backup.  Suburbanites too.

ergophobe

  • Inner Core
  • Hero Member
  • *
  • Posts: 7513
    • View Profile
Re: Heat pumps on the rise after Minnesota passes new energy law
« Reply #2 on: July 11, 2021, 04:18:03 PM »
The fuel-switching issue is interesting. And the fact that they have units that work down to zero F. We're on the cusp of being able to use them for heat. Since it is not uncommon to go into the teens at night and rarely below 25 during the main part of the day, some people do get by with just the air-source heat pump, but when it's in the 20s, they run and run. The overall efficiency of the house is a big factor. The neighbor with a new SIP house has no trouble. The neighbor with an old house with very little insulation has it run non-stop for weeks at a time, sometimes with huge amounts of ice building up on it.

I've also been curious carbon and cost tradeoffs. I think the cost tradeoff would be less here because electricity is expensive in CA, though with the pricing going into effect this year, there will be summer and winter rates for us and the winter rates are a lot lower.

Tiered rates are a big disincentive. If changing to electric heat pushes me into a higher tier, it means those KWH are all at the most expensive rate. If I go into Tier 3, that's 41 cents per KWH. My lowest possible rate in the winter is 23 cents. Google says the average rate in MN is 11.5 cents. So if I went to electric heat, I would be almost 2X to 4X that, which cuts into the savings from a heat pump.

buckworks

  • Inner Core
  • Hero Member
  • *
  • Posts: 1460
    • View Profile
Re: Heat pumps on the rise after Minnesota passes new energy law
« Reply #3 on: July 11, 2021, 06:39:53 PM »
Insulate, insulate, insulate!

Brad

  • Inner Core
  • Hero Member
  • *
  • Posts: 3501
  • What, me worry?
    • View Profile
Re: Heat pumps on the rise after Minnesota passes new energy law
« Reply #4 on: July 11, 2021, 09:21:41 PM »
Insulate, insulate, insulate!

Exactly.  This will serve anyone well, long into the future.

But, having been in the real estate development business, it's amazing to me how many home buyers pay so little attention to this.  They want play area for their drooling spawn, home theatre room, snarfy kitchen, bathrooms big enough for bus loads of people and a three car garage but if you tell them the house is built to be "green" you get a Homer Simpson blank look.

rcjordan

  • I'm consulting the authorities on the subject
  • Global Moderator
  • Hero Member
  • *****
  • Posts: 12952
  • Debbie says...
    • View Profile
Re: Heat pumps on the rise after Minnesota passes new energy law
« Reply #5 on: July 11, 2021, 09:49:03 PM »
>Insulate, insulate, insulate!

And, this makes just about any home built before 1970 functionally obsolete.  I sure as hell wouldn't want to rip out the drywall or siding to insulate. ....And those windows are crap by today's standards.  By the time you add it all up, the place is a tear-down.

Rupert

  • Inner Core
  • Hero Member
  • *
  • Posts: 3077
  • George in a previous life.
    • View Profile
    • SuitsMen
Re: Heat pumps on the rise after Minnesota passes new energy law
« Reply #6 on: July 13, 2021, 07:07:22 PM »
Quote
Tear down

In the UK the building regs don't always make a place better.  Our place in Wales, in a windy (very windy) spot on the coast, has an extension. It has thick insulation in the roof and the walls and actually the floor.  The problem is that the vent requirements mean that the wind that travels through the insulated cavity cool the wall down so much that the 1960s (or 1950s?) wall next to it is warmer.

Also, the venting in the windows means that on a windy day.... it's cold.


I am appalled.
... Make sure you live before you die.

rcjordan

  • I'm consulting the authorities on the subject
  • Global Moderator
  • Hero Member
  • *****
  • Posts: 12952
  • Debbie says...
    • View Profile
Re: Heat pumps on the rise after Minnesota passes new energy law
« Reply #7 on: October 19, 2021, 01:20:59 PM »
UK:Low carbon heat pumps: Everything you need to know from cost to efficiency
https://www.telegraph.co.uk/news/2021/10/19/heat-pumps-explained-everything-need-know-cost-efficiency/

BoL

  • Inner Core
  • Hero Member
  • *
  • Posts: 1059
    • View Profile
Re: Heat pumps on the rise after Minnesota passes new energy law
« Reply #8 on: October 19, 2021, 02:07:52 PM »
>UK

There is a similar scheme already running in Scotland, first come first served until the money runs out. Up to 10K interest free loan, and up to 7500 'cashback' when installing a heat pump. Cashback effectively being a grant. Subject to credit checks of course, and mandatory that your energy performance cert for the house doesn't recommend loft or cavity wall insulation.

Think the newly announced grant equates to about 50,000 installations so not a huge amount considering there's 20M households in the UK- but decent incentive for those who want to get on with it.

When you factor in RHI https://www.gov.uk/renewable-heat-incentive-calculator you can potentially make the money back within a few years.
« Last Edit: October 19, 2021, 02:11:04 PM by BoL »

rcjordan

  • I'm consulting the authorities on the subject
  • Global Moderator
  • Hero Member
  • *****
  • Posts: 12952
  • Debbie says...
    • View Profile
Re: Heat pumps on the rise after Minnesota passes new energy law
« Reply #9 on: October 19, 2021, 02:41:54 PM »
What are you doing about all those stone wallS?  R-value SUCKS.

R-Value | EGEE 102: Energy Conservation and Environmental Protection
https://www.e-education.psu.edu/egee102/node/2062

BoL

  • Inner Core
  • Hero Member
  • *
  • Posts: 1059
    • View Profile
Re: Heat pumps on the rise after Minnesota passes new energy law
« Reply #10 on: October 19, 2021, 03:09:08 PM »
>stone wallS?  R-value SUCKS.

For sure. At mine they're cold to the touch over the Winter months. Suspended floor also needs a look at as floor is also cold. Not any easier that older houses have to be 'in keeping' with the rest of the street so a new external facade tends to not be an option. Regulations...

Looked at internal wall insulation via the same routes as heat pumps (Home Energy Scotland). 10K loan available, 4K back. Quote arrived at 12K and that's not for the whole house, maybe 60% of it. Company that quoted me flat out said they ignore kitchens and bathrooms, too much hassle for them apparently. Doesn't take into account cornices or alcoves or generally any alteration near the outside corner walls. The local council run a means tested scheme where they will grant 7500 and that loan stuff can come afterwards. All seems like a gift but there's obviously some work required after it wrt the original look.

If UK gas prices stay where they're at may all end up the better economical choice.

Tempted by the idea of a GSHP but got a new gas boiler after moving in here a year ago. Seems like insulating is the priority.
« Last Edit: October 19, 2021, 03:10:49 PM by BoL »

ergophobe

  • Inner Core
  • Hero Member
  • *
  • Posts: 7513
    • View Profile
Re: Heat pumps on the rise after Minnesota passes new energy law
« Reply #11 on: October 19, 2021, 03:21:43 PM »
>> venting
>> R-Value

I doubt I'll ever be able to find it again, but I read an interesting article by an engineer who specializes in home insulation. She pointed out that one small hole in a wall dramatically lowers the R-Value of the whole system. The point was that, for example, if you have a big window, it makes no sense to spend a lot of money on super-insulated walls.

Basically, what happens is that cold spot by its very nature cycles warm air past it and so even if it's .01% of the wall area, it might be 5% of the heat loss (I'm making those numbers up, of course). But the point was that you can never really insulate your way out of a leaky wall, even if the leaks are small.

By the same token, modern houses often have horrid indoor air quality and need mechanical systems to circulate the air because they are so tight. So there's that consideration too.

update: I can't find the original article, which had all the math and some good diagrams. This gives the rough idea
https://www.canadiancontractor.ca/canadian-contractor/road-nze-part-three-new-window-technology-delivers-big-r-value-gains/1003280773/

TL;DR
An R50 wall with 10% windows at R3 is not 50*.9 + 3*.1 = R45.3, which you might intuitively think. Instead, it's R15.

rcjordan

  • I'm consulting the authorities on the subject
  • Global Moderator
  • Hero Member
  • *****
  • Posts: 12952
  • Debbie says...
    • View Profile
Re: Heat pumps on the rise after Minnesota passes new energy law
« Reply #12 on: October 19, 2021, 04:11:08 PM »
Long ago, I read that it takes about 6 meters of stone to equal 3.5 inches 9 cm of fiberglass insulation.  AFAIK, there is currently no 'reasonable' interior sheeting material tech that will work adequately without one helluva lot of work (and some interior loss of space).  Air-to-air heat pump output is cool-ish and slow to bring the room up to temp.  It'll need to run much longer than your boilers.   ...And we haven't even discussed old windows.

I foresee a great deal of wailing & chattering of teeth in uninsulated legacy construction.


> if you have a big window

Yeah, my house is 20-25% glass.

ergophobe

  • Inner Core
  • Hero Member
  • *
  • Posts: 7513
    • View Profile
Re: Heat pumps on the rise after Minnesota passes new energy law
« Reply #13 on: October 19, 2021, 04:41:52 PM »
>> need to run much longer than your boilers

As a rough guide, if it's 40F out and an empty house is at 55F, count on 20 minutes to get up to temperature with my forced air furnace and two hours with a somewhat undersized heat pump.

>>chattering of teeth in uninsulated legacy construction

The old, poorly insulated house across the street is a second home, typically unoccupied. Even with the thermostat set low during long absences, when it drops below freezing, the heat pump would run non-stop. That resulted in condensation which froze into huge ice blocks which is how I noticed it was running non-stop. At a certain point the ice touches the fan blades and I can hear it running 24/7 from 100m away.

The new owners got rid of that heat pump and put in another one (it actually looks like a standard A/C unit, though, so I'm not sure). In any case, the original rather large heat pump is now gone.

Short version: they work well in a tight, well-insulated house. But even in our moderate climate where temps rarely go below 20 degrees, they are no match for an old, poorly-insulated house or, at the very least, they need to be sized way up to account for the rapid heat loss.

Rupert

  • Inner Core
  • Hero Member
  • *
  • Posts: 3077
  • George in a previous life.
    • View Profile
    • SuitsMen
Re: Heat pumps on the rise after Minnesota passes new energy law
« Reply #14 on: October 19, 2021, 05:55:17 PM »
Quote
That resulted in condensation which froze into huge ice blocks which is how I noticed it was running non-stop. At a certain point the ice touches the fan blades and I can hear it running 24/7 from 100m away.


The new one probably has a defrost cycle.  Its raw heat to defrost, so is pretty inefficient.  They work best where the water does not freeze.  I cannot imagine why you would have one somewhere that cold, I suppose the rest of the time its cheaper to run than straight elec heating, but the cost of installation must be hard to recoup.
... Make sure you live before you die.