A load approaching 100K for a 4000' house is a ratio of over 20BTU/hr per square foot of conditioned space. That is quite a bit on the high side, especially with an efficient shape like an 80' x 50' rectangle. Even at IRC code minimums it should be about half that.

What's driving the load- a lot of glass or something?

Yes, 14.4 kW (49,147 Btu/hour) is the largest they make. We have not had a single issue with any of the many NextGen boilers that we have installed over the past five years or so. Personally, I think they are by far the best electric boilers available in the States for hydronic radiant heating. However, I don’t know for how much longer they will be readily available in the States as I believe WH Holding may soon discontinue selling them. Right now WH Holding is selling off their inventory for about for $1,200 each boiler. WH Holding is more of an electric utility company and they imported these NextGen boilers from Europe. We use a NextGen 4 kW (13,652 Btu/hour) electric boiler to heat our 2400 sf home.

Posted By sailawayrb on 11 Jan 2019 07:04 PM
We use a NextGen 4 kW (13,652 Btu/hour) electric boiler to heat our 2400 sf home.

That's either a warmer climate or a way better than code-min type of house.

"Typical" tight code min houses in my area come in at about 11-13 BTU/hr per square foot at an outside design temp of 0-+5F. Even some tightened up 1950s 2x4 ranch houses can come in that low, but not much lower.

But if your design temp is 25-30F those code-min houses might make it on 4kW.

I'd personally be hesitant to go with equipment that is being discontinued with uncertain support going forward, even if it's a great product. At some price point I'd cave, but would be assuming the risk of zero support down the line. YMMV.

Well yeah...we build way better than code minimum contractor grade...and especially for our place... After all, a code minimum contractor grade house is the crappiest house that you can legally build!

Yes, if it is discontinued, there is some risk and that is a consideration for sure. But this risk can be largely mitigated by buying some spare parts for the unique components like the heat exchanger and the control module which would only add a couple hundred dollars to the acquisition cost. It is a well designed plug and play hydronic radiant solution that can be easily maintained and repaired if need be by a reasonably competent person. But using electric fuel has to make economic sense for your location...

It will be 80 by 50 with 18 foot sidewalls the living quarters will be 20 by 50 with a 20 by 20 room in the shop these will have 9 foot ceilings and loft above the rest of the shop will have several decent sized windows and 2 10x10 doors and one 12 by 14 in Iowa. I plan to use spray foam in the walls either closed cell or open what is everyones thoughts. I have quotes for geothermal for the building but just can't see spending that much money if I can install a radiant boiler system and use mini split for AC my heating rate would be 6.5 cents KW what do you guys recommend for windows what is your thoughts for insulating the frost footing icf or just use poured wall and insulate it.

thanks

Closed cell foam installed between studs is a waste, In a typical 2x6 16" o.c. studwall a full fill of R6/inch closed cell adds less than R2 to the"whole wall R" performance compared to R3.7/inch open cell foam after factoring in the thermal bridging of the framing.

And the opposite of "green", both in terms of the environment damage of the commonly used HFC blowing agents (which could be avoided using more expensive HFO blowing agent foam), and the amount of polymer per R. Under the Kigali amendment to the Montreal Protocol the HFCs will eventually become contraband, but for now HFC 245fa is the industry standard blowing agent for closed cell foam, with a 100 year global warming potential on the order of 1000x CO2.

Open cell foam is blown with water, ad uses less than half the polymer per R of closed cell foam.

Under the IRC a code minimum wall in southern IA (US climate zone 5A) is 2x6/R20 + R5 continuous insulation, or U0.060 (= R16.7 "whole wall"). In northern IA that would be 2x6/R20 + R10 continuous insulation or U 0.045 (=R22.2 "whole wall".) As it happens R5 continuous insulation external to R20 is not sufficient for dew point control at the cold side of the fiber insulation in climate zone 5, and damaging levels of moisture could accumulate over the winter unless the vapor retardency to the interior were reduced. R7.5 would be the minimum, R9+ would be better. In zone 6 R11.25 would be the minimum, but R13+ would be better. If the stud bays are filled with open cell foam and you cheat the exterior R, using a "vapor barrier latex" primer on the gypsum board would be sufficient, and would still allow seasonal drying. Do NOT use a polyethylene vapor barrier, which has the potential of creating a moisture trap.

A cold climate mini-split can still operate at about twice the efficiency of an electric boiler even at -10F. If going with mini-splits sized for the cooling load, not the heating load, use them for heating too, and operate the electric boiler off a floor thermostat for under-foot comfort and to make up any potential shortfalls from the mini-splits for design-day heat. At 6.5 cents your heating cost per MMBTU with an electric boiler is cheaper than heating with a mini-split in most of New England, where electricity rates are typically more than 20 cents, but that doesn't mean it's really CHEAP to heat a house/building that size. The seasonal average cost of heating primarily with the mini-splits would be less than half what it costs to heat with just the electric boiler, maybe even less than 1/3 if the boiler is used only sparingly.

Geothermal usually doesn’t pass the ROI test unless you are in an extremely cold climate with extremely high electric rates. Geothermal systems tend to also be high risk affairs given their complexity and their need to be properly designed/installed by someone who is competent which if often lacking in that industry. If you need AC, the combination of hydronic radiant and mini splits is a great solution. Just using mini splits alone is a great solution, but you lose the wonderful heating comfort that hydronic radiant provides via a higher MRT (Mean Radiated Temperature). Dana has you fully covered with regard to insulation options.

Yes Geo is a waste now.....You used to get great rates for electric in the winter with Geo but our Public Service Commissions failed us the caved to the electric company....They now give the cheaper rate in the summer since solar has taken off.

We are just starting to work more with Air to water heat pumps.
No dirt work, good down to about 10 degrees then supplemental is needed using electric in the buffer tank. Units are 29,000 btu, 48,000 btu, 60,000 btu.
pumping glycol in to a buffer tank. These systems can be fitter with air units for summer cooling, dhw assist.
I think this is a forward direction for radiant heating, one of the main reasons for looking in this direction.
Dan

What brand of air to water heat pump are you using

We are distributors of Arctic Air heat pumps
Here is a link, http://www.blueridgecompany.com/radiant/hydronic/828/arctic-heat-pumps
Dan