I'm curious to some of the heating and cooling requirements to various R Rated wall and roof system designs to get some ideas of just how much heating and cooling is required in the real world.

What better way of getting some factual numbers is efficient home owners post the State the home is located in, and a bit about the windows, ceiling height, square footage and the tons/btu you installed to keep your home nice and comfortable.

1400 square foot, one story (plus basement) house in upstate SC. The walls are ICF (R-24), including the basement, attic is R-50 blown cellulose. The main floor is insulated to R-19. The windows are Marvin Integrity, mostly casements, Low-E double pane. Ceiling height is 9' 6".

Our design temperatures here are 91 F. in the summer; 21 F. in the winter. I ran a computer program that came up with 9K BTU cooling, and 12K BTU (1 ton) heating. We installed two Mitsubishi Hyper heat mini-splits, a 12K unit (23 SEER) in the open part of the house, and a 9K unit (26 SEER) in the master suite. There is no HVAC in the basement.

So far, we have been able to keep the house very comfortable by running just the 12K during the day, with the thermostat at 76 F., and at night we shut off the 12K, and turn on the 9K. We keep the interior doors open. Temperatures hold within about 1 degree throughout the house, which really surprised me. The highest outside temperature we have experience so far this summer was 98 F., which didn't seem to affect the interior at all. The basement has been holding very steady at 74 degrees. The basement slab is not insulated. We do run a dehumidifier about every 4th day in the basement.

The power bills for a two-person all electric household have been running less than $100, and I think the biggest culprit is the cheap resistance water heater. All of the lighting is LED.

The best feature of the minis, other than efficiency? They are incredibly quiet. You really can't hear them unless the house is dead quiet, and the outdoor units are the same way.

I have no experience with heating yet- get back to me in January!

various R Rated wall and roof system designs

Don't neglect to consider air sealing. It's often the single most important thing.

A not so-superinsulated example:

Central Massachusetts, ~2400' bungalow (circa 1923) w/ average ceiling height of 9', with 1500' of insulated basement w/7.5' ceiling.

Average wall is full dimension 2 x 4, 16" o.c. (~30% framing fraction) ~R15 cavity fill) w/ dense packed cellulose (R14.5-R15), with 3/4" plank sheathing & 9" cedar clapboard, 3/4" horse-hair plaster & lath interior, for a wall U-factor of about U 0.10. Average ceiling is R20 (variably rock wool, fiberglass, half-pound foam, depending on which roof portion). Windows are all ~U0.5 (antique double-hungs + clear storms). Foundation walls & band joist insulated with continuous 3" rigid 2lb polyiso (~R16-17) on the interior side.

Outside design temps: 83F, 1% / +5F, 99% annual HDD: 6500-7000, annual CDD: 300-700

Heat load calculated via I=B=R methods: ~39,700 BTU/hr

Heat load calculated via Manual-J: ~37,000 BTU/hr

Heat load calculated via fuel use methods: ~34,000 BTU/hr

Cooling load never calculated, but south windows have good overhang, west windows are shaded by hill & trees, whole roof is shaded by 2PM in summer- the sensible load is pretty low- best WAG would be ~8000-10,000 BTU/hr peak.

Heating appliances: Modulating gas burner buffered w 48 gallon /reverse-indirect HW heater set to 130F max. Average water temperature during space heating calls is ~122-125F. Average system temp during sustained domestic hot water loads is ~115F. More recently supplemented w/~55,000 BTU/hr (max) ~83% efficiency soap-stone wood stove, operated at an average firing rate in the ~20K range during the coldest months, intermittently during the shoulder seasons.

Cooling: 5 ton ducted York, ridiculously oversized for the load, runs maybe 20-25 hours/year. Standalone 70 pint dehumidifier, uses 400-600 kwh/year.

When it's time to re-roof a combination of exterior foam and replacing/reducing the existing 2 skylights with higher performance will knock ~2000 BTU/hr off the heat load. When PV hits below $2/watt I'll probably drop in ~2kw of grid tied PV (despite the shading factor reducing the uptake to ~60% of the theoretical-possible.) The 9" cedar clapboards are in good shape, won't be replacing them any time soon. The wood stove is installed halfway into the original uninsulated brick fireplace & chimney is on the exterior, and represents both a large heat loss, and a huge performance hit to the wood stove as-is, and the plan is to insulate on the exterior with at least R15 continuous rock wool (hopefully sooner than later, timing to be negotiated with "the boss". :-) ).

jdbree, that sounds like the perfect place for a heat pump water heater.

ricky005 you must also consider the footprint of the house i.e. ranch, colonial etc as this has a bearing on the loss/gain