For sure Tom, I always enjoy threads of this sort. My grandkids should be able to live in what we now consider McMansions +4000 sq/ft & heat the thing with a little 20K btu boiler in the future. We are already close, <10 btu sq/ft is acheivable by many here now & those of us who are really working on it are looking 5 btu sq/ft square in the face now. 1 advance in window tech & we have it. As that is the largest loss. For them (grandkids) choosing a very high quality heating appliance will be important as with these low consumption/run times the unit is quite likely to last 3 times as long simply because it sits & waits for a call for heat for so much of it's life. Heck when we can get it down to 5 btu sq/ft here I think the heating industry (may) just switch over to a roof mount solar HW heating system & the fossil boiler will just be there for backup. Most homes have enough roof space to heat a home that only needs those numbers. Time will tell but we are close already.