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Old 01-01-20, 11:56 PM   #11
gadget
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If things continue how they are in California politically, I would consider your strategy for dealing with planned power outages and keeping your home cool and warm when the grid is down.

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Old 01-09-20, 10:29 AM   #12
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If you are building new, consider radiant floor heat throughout the entire house. I would also look into a geo exchange for any heat pumps so you can go water to water with the radiant. If your building, now is the time to consider it while everything is torn up.

Radiant heat is way more comfortable then scorched air.
Sorry for the late reply !

I concur with gadget. Radiant floor heat is the MOST COMFORTABLE form of heat you will ever experience. The only downside is that when used in a concrete floor, it has a slow recovery from low temperatures.

The other problem with radiant heat is that I do not know of any heat pump suppliers selling designed and tested heat pump sourced system in the US. Mitsubishi does sell them in Australia and New Zealand. So sizing the heat exchanger and controls leaves the OP on his own.

It is hard to calculate, but I don't know if a geo exchange would be cost effective in norther California. It would certainly keep your cooling costs low but you don't have harsh winter.


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If I was building new, the house would be designed around solar heating directly from the sun as a base.
Nothing wrong with passive solar heating, IF you have a good location are willing to have a "non typical" exterior.

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I think multiple heat pumps would be over complication. Its so easy to just move water around from one source. Plus, it may be hard to find a mini heat pump small enough for one room so you would be looking at DIY.
Yes, pumping water for heat distribution is easy (because it has been done for a long, long time), but what about cooling, especially in the bedrooms ?

If the OP does radiant heat, possibly some high efficiency window/thru-wall A/C units (do they even exist ?) might be a cost effective solution.
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Old 01-10-20, 01:38 AM   #13
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Yes, pumping water for heat distribution is easy (because it has been done for a long, long time), but what about cooling, especially in the bedrooms ?
Since you mentioned it, those water source radiant cooling ceiling panels they are starting to use in Europe look very interesting. Dew point control looks like the biggest issue. Reviews have been positive for being very comfortable and quiet vs A/C.

I prefer evaporative cooling vs A/C but that is not for everyone or every region. I prefer the cool moist air vs dry cool. If I was stuck in California and used A/C, I would maybe consider mini splits. That may make it easier to run on a generator when the power goes out since you could just cool 1 or 2 rooms. I'm so glad I don't live there anymore. Good luck OP.

I lived in a small coastal town in central coast california that had mild winters and if I still lived there I would still go with radiant flooring with an air source heat pump and solar heat. A mild vs harsh winter doesn't change the inside comfort affect of radiant flooring vs heating the air.

When I originally read Northern Cal I was thinking Redding or maybe Trinity mountains. Much colder area then the coast above San Francisco. I've lived all over california and Norther Cal gets pretty cold unless your near Humbolt.
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Old 01-10-20, 07:45 AM   #14
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I prefer evaporative cooling vs A/C but that is not for everyone or every region.
Evaporative cooling is great (low cost) but it requires a VERY dry climate.

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If I was stuck in California and used A/C, I would maybe consider mini splits. That may make it easier to run on a generator when the power goes out since you could just cool 1 or 2 rooms.
Excellent point ! I remember reading somewhere that a person set up there house in FL so that one bedroom was sort of an emergency shelter for after hurricanes when the power was out. Window A/C, small refrigerator, Internet, TV, cable AND OTA antenna all capable of being run off of a 2000W inverter generator.
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Old 01-10-20, 10:08 AM   #15
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OK. I live in MN, and agree with the guys that say that a radiant floor is the most comfortable form of heat. That said, with a design day of 40 where you live, I doubt that radiant heat would do you any good. Your body won't be radiating to cold inner wall surfaces, especially since you will be doing a good job of insulating and buying good, low-e windows. Just insulate under the floor better than the usual.

Your idea of a little heat pump in each room is a good one. What you might look into is what is called a "VRF" (variable refrigerant flow) mini-split system, where there is an outdoor unit with a variable speed compressor, and several indoor units. The indoor units are typically small, wall hung units with a fan and a coil, that either heat or cool to their own thermostat. I'd look for the better units which have variable speed fans in the indoor units, because they will often be so quiet that you might not even be able to hear them run.

Regarding the heat gain calculations, the poster above is correct that you must consider heat gain through the walls, as well as solar heat gain through the windows. What I didn't see him say is that it is a little more complicated than that, because those two gains don't happen at the same time. To do it right, you must consider your exposure and time of day. Heat gain through the walls is delayed by maybe 4 hours, but the solar gain through the windows happens immediately. The u factor calculation works for all of the walls based on ambient outdoor temp, but there will be more gain because of the sun heating the south and west walls at different times of the day. Your max cooling load might happen around 4 - 6 PM, and might be based on heat gain from the south wall plus solar gain from the west windows. You might consider mitigating the window gain by shading them, using exterior louvers or retractible awnings.

Regarding the suggestion of radiant hot/cold ceiling panels mentioned above, I'd discourage that. As an engineer, I worked on plenty of them, dating back to about 1980 (more than 1,000 hospital patient rooms) and have worked on a number of chilled beam systems over the years. Yes, they are comfortable until they drip on you, but realize that you will be doing a lot of cooling and reheating for dehumidification, which uses a lot of energy. In my experience, you will just disconnect them.

I'm currently thinking through my next home in northern Wisconsin and coming to the same conclusions. I will be insulating well (R55 walls, R45 under the floor slab, and haven't settled on the roof insulation method yet), heating the floor using a condensing domestic water heater (my design day is a LOT colder than yours), and little mini-split heat pumps in the rooms.
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Old 01-10-20, 10:21 AM   #16
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Your idea of a little heat pump in each room is a good one. What you might look into is what is called a "VRF" (variable refrigerant flow) mini-split system, ...
I am not familiar with VRF systems, but they sounds like a good solution. The cost for the electronics (actually a variable frequency single to 3 phase drive) has come down a lot in the past 5-10 years !
My research, however, show that systems with multiple air handlers are a lot less efficient than those that only have one air handler. I don't know why, unless it is just from the long refrigerant lines.


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I'm currently thinking through my next home in northern Wisconsin and coming to the same conclusions. I will be insulating well (R55 walls, R45 under the floor slab, and haven't settled on the roof insulation method yet), heating the floor using a condensing domestic water heater (my design day is a LOT colder than yours), and little mini-split heat pumps in the rooms.
Friend of a friend built a super insulated house in MI. He actually built double 2x4 walls with ZIP sheathing. The double 2x4 allowed easy placement of standard fiberglass rolled insulation. Kind of tricky to install and trim out the windows and doors.
Another "non typical" wall insulation method is spray foam all the joints from the inside, apply skrim and then blow in cellulose or fiberglass. Much faster so reduced labor cost.
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Old 01-10-20, 10:57 AM   #17
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I am not familiar with VRF systems, but they sounds like a good solution. The cost for the electronics (actually a variable frequency single to 3 phase drive) has come down a lot in the past 5-10 years !
My research, however, show that systems with multiple air handlers are a lot less efficient than those that only have one air handler. I don't know why, unless it is just from the long refrigerant lines.



Friend of a friend built a super insulated house in MI. He actually built double 2x4 walls with ZIP sheathing. The double 2x4 allowed easy placement of standard fiberglass rolled insulation. Kind of tricky to install and trim out the windows and doors.
Another "non typical" wall insulation method is spray foam all the joints from the inside, apply skrim and then blow in cellulose or fiberglass. Much faster so reduced labor cost.
Thanks for the thoughts.

I wouldn't call the indoor units "air handlers." They are maybe 35" wide, 8" deep and 11" high, with a small fan and coil inside. The fan motor is a permanent magnet, electronically commutated, DC motor (ECM), continuously variable speed, and incredibly efficient. You might be able to find something about these systems by searching for Mitsubishi VRF, Daikin VRV, or LG Multi V. Many brands out now. The compressor is also variable speed driven by a similar motor - similar to the AC compressor on a Prius. It is really hard to get more efficient.

Not intending to hijack the original poster's thread... but so far, my walls will be ICF with 6" of additional foam, so 6" reinforced concrete plus 11" of continuous foam (no thermal bridging or joints for air leakage). Wife wants it tornado safe.
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Old 01-11-20, 09:41 AM   #18
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Thanks for even more ideas, guys!

I think I'll go with good insulation and (almost*) completely electric: a mini-split per bedroom, multiple mini-splits in the "big room", all powered with solar and a battery, potentially with VRF if that's more efficient. *Then I'll have a gas fireplace mostly for looks and for a few extra cold nights (it got down to 38F yesterday). For the extra hot days I'll bring out some floor fans.
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Old 01-11-20, 11:42 AM   #19
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Thanks for even more ideas, guys!

I think I'll go with good insulation and (almost*) completely electric: a mini-split per bedroom, multiple mini-splits in the "big room", all powered with solar and a battery, potentially with VRF if that's more efficient. *Then I'll have a gas fireplace mostly for looks and for a few extra cold nights (it got down to 38F yesterday). For the extra hot days I'll bring out some floor fans.
Good choices. Get a gas fireplace that is efficient at heating the rooms, not one that is just made for looks. That way you will have a good source of backup heat if you lose power.

And, for those cold nights, a very comfortable, effective and efficient way to handle them is with an electric blanket under your regular blankets.

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