Building ICF colonial 3500 sq ft - solar tempered in Cleveland.  Will put in geothermal with spray foam unvented attic.  Considering concrete floors - but not hydronic heat.

My question is - what can I do to maximize the COP?  I have heard that short run times are bad - so I was thinking that if I had concrete floors (i.e. thermal mass) that my run times would be longer - and therefore i thought my COP higher.  Is this true? 

If longer run times are better - can I program the thermostat to stop heating at night and then go on at 5:30 am for one long run to maximize efficiency?  (I thougt this would also allow me to take advantage of nighttime electricity rates which I believe will be coming to my state sometime.

Basically since I am building from scratch I want to know any ways I can design the home and system from the start to maximize my performance.

Thx in advance.

Todd

Thermal mass is always good to add. I'd be worried that the incremental increase in COP would never pay for the incremental cost of pouring and supporting concrete floors.

OTOH, if you do decide to go with concrete floors, carefully consider radiant. Properly designed it can give a better COP than hot air, and greater comfort as well. I considered it but ruled it out since my north Florida heating season is pitifully short.

Also there is a major constructability issue with ICF walls and radiant tubing. ICF needs a bracing system to hold walls plumb, square and true during pour and while concrete hardens - that bracing system is generally screwed to the floor in the inside. Those screws pose a serious risk to radiant tubing. It is possible to brace from outside, but that is hard on the ICF crew, and they will resist that.

Establishing and marking "no screw" zones over tubes is a possibility, but perfection in planning and execution would be essential; it would only take one holed radiant tube to make you very very sad...

I surfed that issue extensively and asked around and never got an answer that felt adequate. Someone here or over in the ICF forum here may have an answer - I didn't know about this site then.

Setback thermostats are nifty but likely overrated in case of a big ICF house whose tightness and thermal mass should result in small temperature drops overnight. Moreover, if a two speed system is able, most of the time, to meet heat and cool loads on low speed, but is kicked into high speed during setback recovery, a likely result is a net decrease in efficiency and increase in cost owing to the reduced efficiency of the system running at high speed. Even worse is if backup electric strips kick in during winter recovery - that is virtually guaranteed to trash any savings from a nightime setback.

If rates are low at night, I'd think you'd want to run MORE then, not less. Devising a system able to store heat made during off-peak time might work, but the increased cost, volume and complexity would have to be weighed against any possible savings - difficult in a small residential system.