Thank you very much for your insights!!
So the way I understand is I should tell my HVAC guy what insulation we are going with because in having a more efficient home, I would need less capacity on heating/cooling appliances?
I had originally thought about infloor for the basement also but I'm not sure as the layout may be a little tricky with putting up walls and anchoring them to the floor.
If I were to do that and have a boiler, what are the options for heating/cooling the remainder of the house?
The builder is a custom home builder, will use any contractors we wish to, and has been awesome to deal with so far in our meetings. Also his business partner is the carpenter. This has been very helpful as the design guy can make it look good on paper, but the carpenter knows what is practical and makes the most construction sense.
The HVAC contractor needs to understand the insulation so he can plug all of this into his heat loss calculator. While things are changing -- the vast majority of HVAC people don't have much experience with foam and top equipment. The industry is rapidly changing -- houses are getting better and manufacturers are now coming out with smaller output heating devices. But, old habits take a long time to change .. die hard.
HVAC companies commonly just replace what's in a house when switching out a heater or AC ... w/o ever checking the heat and cooling load on the building. They ask the homeowner if it worked OK ... most homeowners have lived with oversize equipment forever --- they don't understand how much of a difference having the proper equipment can make. Another problem is the manufacturers .. even if the building needed only 50k -- if the smallest unit was 70k ,,, what could you do?
Building new is not much better. Too many HVAC people use "rule of thumb" calculations based on SF. New house will be 2000sf .. needs 400-500 a ton of AC. Put in a 4T unit ... homeowner likes it cold ... put in a 5T. I did a 2k sf barn conversion with foam and SIP's -- it has 2T of cooling.
Foam eliminates air leaking .... air leaking is a huge issue with heating and cooling a building. Insulation only works w/o air movement. CC foam also gets you about 7R per inch. The first inch of foam is amazing ... people don't understand how much a thick wall of fiberglass batt insulation can leak .. not getting the R value. I think more work needs to be done on finding out the real R value of various building systems ... most new houses still leak. And the new building systems that need to have tape seal everything up ... I wonder .. what happens in 20 years of heat cool cycles on tape? if it fails there goes the R value if batt.
So it's very important to have someone do the calculation correctly and not be afraid to follow it. The other item is to not design something for a possible one off event. In other words: in the midatlantic you don't want to design an AC system to maintain 70 degrees at 105 outside temp .. because it hit that temp once 10 years ago. It's often better if you are on the edge of two different sizes to see if it's not better to go with the smaller size. Design for 72 degrees -- or even a two day event at 74 ... 74 degrees at low humidity is very comfortable. oversized equipment often can never get the humidity down .. 70 degrees at high humidity can waste energy and not be as nice as 74.
Another factor people forget when building well -- the operating costs drop. So the cost of maintaining a space at a higher temp is not as great as one not built as well. So while radiant is not a system that works well with changing the indoor temp all the time .. it's a great part of an overall building envelope when temps are maintained -- this is especially true with cheap natural gas.
I'm in the process of rebuilding an old sone building from the 1870's and adding on to it. I poured a new lower level slab and installed a simple radiant loop system based on the 250 max at 8" loops -- it's well below grade so I did the 8". Most people use 12" everywhere .. I tend to use more loops and use cooler water .. that's just how I do it. It's a typical 4+ inch slab with proper base and drainage -- vapor barrier -- 2" of foam and the tubes tied to the grid. I use a slightly high PSI mix -- in my case its going to be a finished floor and we used Sika color on top. It's easy enough to lay out the tubing to stay clear of the framing -- in reality the nails are not going to hit the tubing. I keep them pressurized with a gauge. Some will say you need to keep the mesh in the middle -- but I have never had any issues with an inside slab ... Many of the newer designs use a plastic grid system to hold the PEX -- and that's at the bottom as well. Properly insulated -- the heat will go up tot he space w/o issue.
In this house I am using "warm board" for the finished wood floors and bathroom with tiles.
Yes -- it can all get expensive. HVAC is one item most don't think about -- but having a comfortable efficient quiet house is my goal. While I have never done it -- one member on here has used buried insulated pipe to heat a house and garage with one boiler. Again -- it's all a question of heat load. Your's is attached .. so that's easy. You only get one shot at it and if this is a long term house ... it's worth thinking about. One boiler could heat the garage and warm the floors --- add some plates or staple up for simple warming of the floors of the kitchen and baths.
