Posted By sbeausol on 01 Aug 2012 03:46 PM
They did not do a manual J, they simply estimated, which I've heard is common, and from the sounds of it would cost me $10k. The sales guy indicated that 4-ton would be better in case I ever decided to finish the basement (another 2000 sqft - although I would only ever finish half of it). They will do 'final load' calculations as part of the $800 in permitting fees. I've gone through the MA saves energy assessment for which they will provide extra insulation in my attic and sealing for about $750 which I plan to do. I've been planning on getting my own energy audit, but I haven't gotten around to it.
I have another company coming in next week to quote me out so we will see.
It's a bit frustrating that it is so challenging to pursue the most environmentally friendly HVAC solution....
I wonder what "simply estimated" really means?
To me it means "wild ass guess, to the high side just to be sure they don't call me shivering and irate at 5AM on the coldest day of the year". Crusty old schoolers will eyeball a place and if the windows are decent and its' not too drafty and use a crude rule of thumb along the lines of "25BTU a foot, times a couple thousand feet, yer talking 50K, so 48K will probably be enough", but that rule of thumb reliably oversizes, often by more than 50%. So if your true heat load is 32K (under 3 tons), that rule of thumb puts you in the 48K range. 48,000BTU/2100 comes to about 23 BTU/foot, so that feels like the very common but WRONG rule of thumb used. As a rule real heat loads are lower than that- it doesn't cost the installer more to oversize it,by 50% but it costs YOU plenty. If it were a gas furnace the cost difference for 50% oversizing would be a few hundred at most, but with GSHP at these rates it's more than ten grand. Any geo pro worth paying would calculate it more closely- these guys seem to be fishing for suckers. Without a room by room heat load calc the odds that they'd get the temperature balance & ducting right is pretty limited too.
It shouldn't cost more than a few hundred to do an independent room by room heat load calc- far less than the cost of an "extra" ton of geo.
The additional heat load of 2000' of heating an insulated sub-grade basement won't be anything like another ton either, not even close, unless the first floor is ultra-tight and well insulated that the basement stays below 50F all winter (unlikely). Insulating the basement walls to R12 with 2" of closed cell foam would run about $3.5-$4K, and putting a 2x4 wall with batts on the interior side of the spray to bring it up to the R20 range still won't be anything like the $11.5K they're asking per ton. Simply insulating & sealing the basement would raise even the un-heated basement temps into the 60s, lowering the whole house heat load by more than half a ton, so it's worth doing under any circumstances or future plans. At that point heating the basement to 68F up from 62F or 65F adds only a small fraction of a ton to the load.
With modest improvements to the building you're probably looking at something on the order of 2.5-3 tons of heating load, which would make a 4 ton system truly outlandish. With my mostly-conditioned (~65-67F in winter) basement I'm at about 3600' of conditioned space, and have a measured +5F heat load of less than 3 tons. With planned improvements it should be closer to 2.5 tons after correcting known deficiencies. I suspect fixing the thermal shortcomings of your ranch house will prove both easier & cheaper than my 1-1/2 story bungalow. (cood b rong , offen am.)
It's not always clear that geo is the most environmentally friendly HVAC solution- it really depends on the local grid sources and your actual (as opposed to advertized) real seasonal COP. Sometimes condensing gas is a more environmentally benign way to go, but with the current MA grid sources it's something of a wash. Lowering the load with building envelope improvements is usually the most environmentally friendly HVAC upgrade, up to a point. In retrofits peeling off a full ton from say 32K to 20K might be prohibitively expensive, but that's not always the case in new construction. At 11.5K per ton you would have a pretty good budget for load reduction though, and a ton of load reduction has no operating cost- only increased comfort.
It'll be curious to see how the other proposals compare, but don't be surprised if somebody proposes a 2.5 ton system and another proposes 5 tons. Just make them rationalize how they got to those numbers, and keep a close eye on fudge-factors like understated R values and outside design temps 10F or more below the
ACCA Manual-J numbers (note Gloucesters' heating outside design temp is +5F, so Essex won't be more than a degree either way from that.) Those contractors who offer to do a real heat loss calc up front (even if it's for a fee) move to the head of the list.