ICF house to efficient.

draftpower

I have sort of created a pickle.

I have built a 1450 sqft house with full basement and a 750 sqft garage also in icf. This is attached to my current house sort of as a duplex(living area is for my mother) The top floor has only 1250 sqft heated (corner room is the enclosed porch/sunroom/entry buffer). The heat is radiant floor which is a composite steel/concrete slab. So very high mass as there is 135 yards of concrete. The garage is also a heated slab with 3" of xps underneath.

The walls are r33 foam and ceiling r60. Zero air penetration due to concrete 6" wall in between the foam.

Basement is not to be heated but radiant heat from ceiling and good insulation I doubt it will drop below 60.
If I finish a room later radiant baseboard be used there.

So doing manual j calcs are showing 12000btus Hr at 0f for the house and the garage kept at 50-55 is going to be less than 7500. I have been warned that my numbers might be high as my icf supplier has stated that tradition manual j calcs have always ended high and he has never had someone do a garage in it, they normal do 2x6 stud walls.

So the problem. Everything is way to big. I originally was planning on using a HTP Phoenix light duty. We have really hard water here and traditional hwh (electric) have not done well due do mineral build up even with a softener. Our hp WH (GE geospring) has done well as in hp only mode it does not do this. I am afraid of short life due to the constant heating of the well water.

So I switched to a weil mclein gv90+3 but at 56000 it way to big. I was hoping to avoid modcons due to high maintence but may have to go that route.

Note1 venting/air of the heating appliance has to be 3" PVC. It's very hard to change now due to being a 7"thick steel/concrete slab with pex running thru it.

Note2 Cooling is a Mitsubishi 15k mini split with hyper heat. Shoulder season usage can be eliminated or greatly reduced by using the heat capacity. I would have to have a seperate dhw heater however then.

Any suggestions conventional or unconventional?

Thank you
Jay

Rich_49

Jay ,

Where are you located ? I have tackled this issue previously with very good results . 4000 sf ICF home ( 31,000 BTUh ) @ -7*f in Ann Arbor Mi , <50.00 per month NG bills for heat hot water , cooking and laundry .

Your situation is actually more challenging being smaller loads . You're on the right track with the Light Duty but much depe3nds on loop lengths and requirements . I'm sure we can help but it will require some open mindedness on your part .

How is the existing house conditioned ?

draftpower

Location is north west Indiana in the country. Straight west of Lafayette near the Illinois border on the edge of the prairie. The wind nearly always blows here which is why there iS several several wind farms in the area.

Existing house is mainly heated with a small Jotul wood stove. Propane 96% furnace and central air use about 350 gal of lp a year. Dhw is a hpwh. I have thought to do a radiant floor in the kitchen which is adjacent to addition but that is down the road. The furnace is 30' down from the utility chase to the addition. Existing house is 2x6 walls w fiberglass and r60 in the ceiling.

The addition has 5 loops of radiant barrier pex a. Each loop is 267 feet long. 3 loops on one zone/manifold, 2 loops on another. Manifolds are 15' from were the heating appliance will set. Loops set in 18" from perimeter to increase btus were people actually walk

Garage has 2 loops( don't remember exact length right now but they are identical and somewhere near 250'. Laid heavy were I may work on cars/in front of benches and spaced out near edges/doors. 45' from heat to manifold on this zone.

Open minded as long as it's is durable and vents with PVC.

Thank you.

Jamie Hall

What, if any, infiltration/air exchange are you allowing for? You do need to have some, or your indoor air quality will be poor. Minimum of one air change per hour (two to four is better). This can be a problem in a heavily insulated house...

Rich_49

Jamie Hall said:

What, if any, infiltration/air exchange are you allowing for? You do need to have some, or your indoor air quality will be poor. Minimum of one air change per hour (two to four is better). This can be a problem in a heavily insulated house...

Jamie ,

I am interested in your recommendation for a min of 1 ACH and the suggestion that 2 - 4 is better . Could you elaborate on this ?

Please keep in mind that a code minimum house built to today's standards should have ACH of no more than 7 ACH50 , and I actually believe that number has been lowered in the 2015 IECC .

Larry Weingarten

Hello, Do you have some sort of air to air heat exchanger? With such a tight home, you likely need it to maintain indoor air quality. Also, this will reduce your heating load even further.

Yours, Larry

Jamie Hall

Rich said:

Jamie Hall said:

What, if any, infiltration/air exchange are you allowing for? You do need to have some, or your indoor air quality will be poor. Minimum of one air change per hour (two to four is better). This can be a problem in a heavily insulated house...

Jamie ,

I am interested in your recommendation for a min of 1 ACH and the suggestion that 2 - 4 is better . Could you elaborate on this ?

Please keep in mind that a code minimum house built to today's standards should have ACH of no more than 7 ACH50 , and I actually believe that number has been lowered in the 2015 IECC .

See also Larry's note. There is an on-goiing debate over how many air changes per hour one needs -- and, of course, it varies with occupancy. The figure I gave comes from my own experience -- from some years back! -- with various occupancies and constructions, including superinsulated 100% solar houses. The problem, of course, for a residence is that many of the materials used in the residence off-gas, sometimes for years, and they may not be all that healthy. Then there is cooking -- particularly with gas, but even with electric. Then there are the occupants themselves... in some areas, you may also have problems with some gasses from the ground, such as Radon.

Larry's answer is the solution, of course -- if you are going to build a super insulated house, provide controlled air exchange with a heat exchanger (I prefer to use sensible heat only; a little less efficient, but real advantages to air quality as well as simpler). Properly done, the impact on the overall heating or cooling efficiency of the house is not great.

BigRob

What about a large reverse indirect for DHW and heat storage?

draftpower

I am incorporating hrv ventilation into the house. The basement will be ventilated as well. Hopefully next year there will be solar air heaters to preheat incoming air.

draftpower

So it looks like the thread has been derailed by talk of hrv and such

Been researching the uft80/WBRULP080W and the Phoenix light duty.

The reverse indirect comment by big rob got me thinking. What if I install a phoenix as a boiler and run a small indirect off of a primary loop? That would solve the issue of precipitating out solids in the tank but would it kill the efficiency? To bad they don't wrap tubing around the tank to provide a pseudo demand hwh. Also will the tanks 3/4 taps flow enough? I have to get my t ext book out and do some math.

With the UFT80 it appears the it is adventagious to direct pump. Every thing I have been privy to has been primary/secondary with a circulator on each zone. Not really familiar with direct pump method and have reservations on flows short cycling if all the zone and the indirect are calling for heat at the same time. Also do some controls allow for my floors to drop a few degrees in temp before calling and then only pumping/reduced fire rate for longer periods of time to raise efficiency and reduce short cycling?

BigRob

I’m in CA and power can be pricey. This is why I prefer a single variable ecm pump feeding zone valves.

Check this out:

http://www.thermo2000.com/content/en-US/s2_produits/optimizer.aspx

If I was to do it again, I’d go this route with zone valves and a good non-condensing boiler. It doesn’t get too cold in SF. As is we could use some buffering for the floor slabs, even at 20% modulation. I have anti-cycling set up ok, but around 50 gallons would be great. As is we have a separate regular indirect for DHW- just more stuff to break down and leak.

Harvey Ramer

Check out the HTP Versa Hydro. It's a high efficiency water heater with a space heating module built in. The water heater acts as a buffer tank to the heating system.

Rich_49

You could simply use a Pioneer w/ a FPHX and a circ for DHW . Basically making your own Versa Flame . Too bad very few realized the value of that unit , we installed several with stellar results .