Hi, I am working on plans for a single story ranch house in Westcliffe Colorado. Around 1500 sq ft for the first floor with a 1500 sq foot basement. Part will be finished and part will be a garage/shop/storage. I will use ICF for the foundation. The walls will be 2x6 somewhere from R30-40 when finished. The west wall will have quite a bit of glass. I will have a high efficiency fireplace (77%) for supplemental heat. We plan on staying there from June through October and probably a couple weeks during the winter after we retire. For the next few years we will go up there 4 or 5 times for 1 week stays. I am seeking ideas on heating and cooling. At the current time propane is $2.15 gallon and electricity is .16 kWh Here is Westcliffe’s climate data: https://weatherspark.com/y/3523/Average-Weather-in-Westcliffe-Colorado-United-States-Year-Round My original plan was a propane fired boiler (with possible active solar heating) and radiant heat in the basement floor and first floor. I see two problems here. One it will probably take several days to bring the slab up to temperature though the first floor should rise somewhat quicker. I guess one way around this is an Internet controlled boiler that I could turn up a day or two before I head there. Now if had solar panels providing the heat for the radiant floor I could leave the temperature higher when I wasn’t there and it wouldn’t take so long for the place to heat up. The second issue is the basement floor. If I decide (or the next owner decides) to finish the rest of the basement how do you keep from puncturing the Pex with nails as you install the sole plates? I could layout future walls in advance and leave Pex out of those spots but then I would be stuck with a particular floor plan. For cooling I would have mini splits with zones for the upstairs bedroom, great room and kitchen. Then another downstairs for the bedroom. I am also considering a high efficiency propane furnace with ductwork running in the basement ceiling. I could have vents for both the basement and first floor- maybe a multizone system. I will also need air conditioning so probably a central unit. I could also use mini splits for both heating and cooling but would need some kind of backup heat source. Not staying there year around makes the decisions more difficult though I still don’t want high utility bills when I am there. I would prefer to leave the cabin at about 40-45 degrees year round as opposed to winterizing it but the power goes out in this area quite often so I would probably need a standby propane generator as well. A small solar system with batteries would work but I am not sure how cost efficient that is either. Any comments or suggestions on what would work best for me and approximate costs? “Free heat” from the sun to run the radiant system is appealing because all it would have to do is keep the place around 45-50 degrees. Then when more heat is needed the propane boiler could come on. Thanks

Getting to the optimal solution starts with a room by room and whole house load calculation. Yours is a better than code house, with lower than typical loads, which gives you some options. The notion that mini-splits would need backup is not well founded- it's a matter of specifying the right mini-split. They are MUCH better now than they used to be!

With an open floor plan a couple of cold climate Fujitsu mini-splits would probably do just fine. At your altitude the capacity has to be derated to about 75% of the nameplate BTUs. The Fujitsu mini-splits have a "Minimum Heat" mode which sets it to 50F heating for freeze protection.

A 1.25 ton 15RLS3H is good for 16,000 BTU/hr @ -15F at sea level, and thus good for about 12,000 BTU/hr @ -15F at 7500', assuming 70F indoors. At 50F indoors -15F outdoors you're looking at a mere 65F temperature difference. At 70F in/+5F out the same delta-T, those units are good for 20,500 BTU/hr each, ~15,000 BTU/hr derated for altitude, so in a tight better-than code home you might do OK with just one, but with a pair of them it would take a fairly crummy house to run out of capacity. Your 99% outside design temp is something like -11F.

Since you're designing this better-than-code house you should be able to keep track of the heat load numbers.

If central-ducted distribution is a must, 2 ton 3 zone Mitsubishi 3C24NAHZ is good for 25,000 BTU/hr @ -13F, or about 19,000 BTU/hr derated for altitude, and can use a 1.5-2 ton full sized MVZ air handler for the primary zone. The 1.5 ton air handler is good for 20,000 BTU/hr heating at sea level provided it has enough compressor behind it so it's output even derated would probably be enough at 50F indoors, -15F out. The Mitsubishis will shut down at about -20F (unlike the Fujitsus) but the MVZ air handlers have resisitive heat-strip backup option (unlike wall coil mini-splits.) . Mitsubishi has a "Smart Set" mode that allows setting the temperature to 50F for most of their systems, but I'm not sure if that works with their MVZ air handlers the way it does with the wall-coil heads.

The basement can probably be heated with a half-ton Mitsubishi FH06, or any cold-climate 3/4 tonner, but it's not necessarily worth the upcharge for just a basement. If the domestic hot water is propane-fired, a small hydronic loop off the water heater might be the "right" solution there, but with cold-climate multi-split a half ton head in the basement for one of the zones wouldn't be a huge cost adder.

Both Fujitsu & Mitsubishi have Wi-Fi control options that would allow you to change the settings remotely.

With 16 cent electricity either vendors' cold climate heat pumps will beat the operating cost of $2 condensing propane by quite a bit- half or more during the shoulder seasons, and still cheaper at -15F.

Thank you for the very detailed response. Littleboss

Quote: If I decide (or the next owner decides) to finish the rest of the basement how do you keep from puncturing the Pex with nails as you install the sole plates? One way to avoid puncturing the Pex with nails is to place a 6" thick slab and then install the Pex low in the slab. The extra mass may take longer to warm up but that would be better than creating leaks. The continuous thicker slab may eliminate the need for footers under interior load-bearing walls.

Is the Pex normally placed at the bottom of the slab? If so even in a 4" slab the Pex should be out of a nails reach. The concrete nails that I have used in the past were 2.5" long

Thanks

I suppose I could also go ahead and have Pex installed in the slab even if I didn't plan on using it right now. Then later on if I started spending more time there in the winter add a propane fired water heater

I just used a premium construction adhesive under the bottom plate of a wall over a pex installed slab.

You can easily see where the pex pipe is with a Thermal Camera. They are only ~$200 now and work great.

Many would say doing an ICF house with out continuing to the roof is a waste.

Good luck sounds like a nice place.

Posted By newbostonconst on 13 Dec 2018 05:04 PM
You can easily see where the pex pipe is with a Thermal Camera. They are only ~$200 now and work great.

Many would say doing an ICF house with out continuing to the roof is a waste.

Good luck sounds like a nice place.

Thermal camera is a good idea. Thanks. I am choosing ICF for the foundation for several reasons. One the basement walls will only need drywall not studs, insulation and drywall. This will save lots of time and labor. Second I suspect the basement will be well enough insulated that it will not require conditioned air, or at least not very much. I am not using ICF for the first floor walls for several reasons, the main one being by the time I build an ICF wall and add half logs to the outside my walls would be way to thick to be attractive. If I wanted a stucco finish or adobe look I would go with ICF all the way. Thanks for the input.

Posted By newbostonconst on 13 Dec 2018 05:04 PM
You can easily see where the pex pipe is with a Thermal Camera. They are only ~$200 now and work great.

Many would say doing an ICF house with out continuing to the roof is a waste.

Good luck sounds like a nice place.

Depends on the location with the roofing.

If you're someplace prone to forest fire or high winds (Tornado Alley, Hurricane Alley), yeah, a concrete roof makes more sense in terms of long-term durability.

Other places, going with a SIP or stick-frame roof with sufficient insulation will yield an acceptable outcome without breaking the bank.

Posted By littleboss on 13 Dec 2018 02:36 PM
I suppose I could also go ahead and have Pex installed in the slab even if I didn't plan on using it right now. Then later on if I started spending more time there in the winter add a propane fired water heater

Also on the "How do I make sure I miss the Pex".

It's called "documentation".

Get GOOD, HIGH RESOLUTION pictures.  Get some video.
Before you dump the concrete in, take measurements on the Pex runs and graph it out.
It won't be "perfect".  But it's better than drilling down and hearing a loop depressurize on you.

Going with a slightly thicker slab and placing lower in the slab (especially if the slab is fully insulated on the bottom and edges) is a good call as well.

Posted By Dilettante on 13 Dec 2018 09:14 PM

Posted By littleboss on 13 Dec 2018 02:36 PM
I suppose I could also go ahead and have Pex installed in the slab even if I didn't plan on using it right now. Then later on if I started spending more time there in the winter add a propane fired water heater

Also on the "How do I make sure I miss the Pex".

It's called "documentation".

Get GOOD, HIGH RESOLUTION pictures.  Get some video.
Before you dump the concrete in, take measurements on the Pex runs and graph it out.
It won't be "perfect".  But it's better than drilling down and hearing a loop depressurize on you.

Going with a slightly thicker slab and placing lower in the slab (especially if the slab is fully insulated on the bottom and edges) is a good call as well.

The problem with documentation is I am in Texas and can't be there all of the time when the building is going on. I will expect the builder to email me daily updates with pix and I can hope for details as you suggest but will not count on it. There aren't any trees around the place so a fire isn't a problem. It a semi- desert climate. They do have an occasional tornado in CO but way more here in Texas