We are planning a new home. I recently attended a “home/builders show” to establish some contacts and get some ideas. I visited both HVAC booths and insulation booths. Some of the insulation contractors told me they could not advise on the type of insulation they would propose for my plan until I had an HVAC plan. Some of the HVAC contractors said the exact opposite, they could not propose a plan (type of HVAC system) until the insulation was finalized. This makes a little more sense (due to required heat loss calculations) but this should be a issue on sizing, not design. We will be building in a isolated area, so I want to get this as efficient as possible. Any comments?
Discussion Forum
Discussion Forum
Up Next
Video Shorts
Featured Story
The DeWalt 4.5 in. — 5 in. grinder has variable speed control (six speed settings), a safety system that shuts down the tool if the blade binds, and a brake that stops the wheel after the trigger is released.
Featured Video
Highlights
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Replies
Comments
Remember the name(s) of the insulation contractors that could not advise you until you had an HVAC plan. Then be sure to use someone else.
To design an HVAC system without knowledge of the details of the envelop construction, or before they are developed is, to say the least, iladvised.
Some of the details of the floorplans should account for the type of system to be used. For instance, providing for the change in floor height a hydroniic infloor system would require or the need for a chse and trusses betwewen floors to accomodate ductwork. Ultimately, the plans will be need to be worked concurrently. Decisions in one area will affect the requirements in another.
In my experience, the type and amount of insulation in a structure will depend on the climate, the budget and the goals of the owner, not the HVAC system.
I didn't know that hydronic systems use ductwork.
The comment
I made "For instance, providing for the change in floor height a hydroniic infloor system would require" is separate from the second part " or the need for a chase and/or trusses between floors to accomodate ductwork".
Bad typing aside, no mention for a hydronic system needing ductwork.
The point is, whatever the system of choice, a smart house design will provide accomodations.
No worries, man. I read a little too fast is all connecting words in the wrong ways.
Which comes first?
Bozo,
You need a team approach to home design. It's impossible to design an HVAC system until you know the size of the house, the insulation levels in the walls, the size & orientation of the windows, the window glazing specs, and the home's airtightness goal.
It's impossible to design a home without knowing the type of HVAC system that will be installed, so that duct runs, piping runs, and the location of the mechanical room can be planned for.
So the designer and the HVAC installer have to work together and learn how to communicate!
I tend to agree w/ Tim ... lose the insulation guys that think the HVAC system will dictate their insulation work. You are correct, the HVAC system needs to accomodate the insulation system. However, given minimum codes and reasonably expected insulation levels, an HVAC system type and layout can be formulated prior to final insulation levels.
Often with new high levels of insulation and high performance windows, ductwork may no longer need to be run to the exterior wall under the windows. There has been a bit of a shift in the design philosophy here. This MAY be affected by climate (i.e. really cold climates may not allow this).
If you ask HVAC contractors questions about duct sizes ... pick the one that says it depends on room size ... he's the one doing room by room heat loss calcs, the others are just using rules of thumb. Ditto e.g. the furnace/AC size ... if they say ... oh about an 80,000 btuh should do it ... lose him. If he says that it will depend on the calcs, then choose him.
Maximize your insulation in your planning. Minimize glass exposures to the east/west ... or treat them with special glazing if you can't avoid them. Spend as much as you can afford on window thermal quality. Minimize your house size (don't get sucked into overdesigning like most people do).
Now you would be ready for the smallest (read lowest cost) HVAC system and maximum comfort. Where are you located?
Only the goverment does it THAT way
A few years back our government came out with a $10,000 grant if you converted to geothermal...Also grants for insulation upgrades. You had to go through before and after efficiency testing to qualify. (blower door, etc)
The big problem was that our geo unit was sized according to the "before" figures, but now operates under the "after" conditions.
Sure is a lot cheaper to run than the old oil furnace, but doesn't run long enough to produce much hot water in the winter, especially if we have the new fireplace insert going.....