Are there diferent heat calcs for differnt insulation?

Reinvent

I am managing a complete gut rehab of a 2600sq ft , 2 story, single fm house. Its going to have HVAC in the basement to supply the first floor and a HVAC in the attic for the second floor.
The HVAC installer came by to do measurements for a heat calc and to disscuss details on the install. I asked him if the type of insulation used would affect the results of the heat calc. He said not really.
I am looking at spray foam for the insul. I am hopeing I can sell the extra cost of the foam to the owner by saying we can downsize the HVAC unit a little.
Is this a reasonable assumption?

Weezbo

well, let me put it to you like this,....

i have r 71 in the lid...i checked on the average heat loss for my home and annual estimated costs on a government site, my annual costs are less than 20 % of their numbers. any one who knows any thing about insulation will swear up and down that there is no benifit from any r value over like r-48 or so....well. eh...? whassdadeal? sorry about that maybe i havent answered your question.i am not the installer of the hvac so who know what your ideas are on insulating the pipes etc....it is as though you are asking me to go out to the shop truck after my crystal ball,...it is cold today and i am getting older by the min...dont ask me to do it...ok?

hr

True foam R value

is often misrepresented, I feel. A local spray Isoneyne guy claims 1/2" equals R- 20! When I question how he comes up with that number he explains..

"You can put 200°F water is an 1/8" thick styrofoam coffee cup and it doesn't burn your hand! Try that with fiberglass." Ok then

I still paid the additional and had him spray 4" in my shop ceiling

What spray foam excells at is sealing against infiltration. In older homes, and even brand new construction, this can be a huge, and hard to calculate, number.

Walk around newly sprayed (rough framed) buildings and you will see that foam ooze out of cracks and gaps the thickness of a business card!

I suspect this has a lot to do with the performance of spray foamed structures compared to fiberglass batts.

This R value claim has been a BIG issue with bubble foam products under slabs, also. Looks like most manufactures have backed down to a more realistic R 1 for 1/2 thickness bubble foam products.

Sure gets confusing when you hear the fiberglass vs spray foam issue debated.

hot rod

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Constantin

It all depends...

... if the installer does the insulation right and seals the house air-tight, it makes no difference whether he's using pink panther, cellulose, dense-pack cellulose, icynene foam, etc. they're all about R3.7/inch.

Corbond and other closed cell polyurethane foams are much more effective at about R6.5/inch, while extruded polystyrene gets up to R5/inch. Polyisocyanureate (sic?) is all the way at R8/inch. Of these three, only the corbond/closed cell polyurethanes can be applied in situ, the rest are bought as boards and must be sealed in place.

So what makes in-situ applied foams and dense-pack cellulose so interesting? If the GC builds the home like most builders do, there are air leaks everywhere. This is where dense-pack cellolose and in-situ applied foams come into their own, stopping heat conduction and infiltration. Closed cell polyurethanes are my favorite because they keep expanding (sealing holes shut) and add a lot of stiffness to walls. Plus, they have a very low perm rating so you won't need a vapor barrier.

If you look at the output from a quality heat loss/gain calculator, they'll list out the infiltration as a separate line item. In our home it was as high as 20% of the total heat loss/gain. When you stop that infiltration, you can downsize ducts, equipment, pumps, etc. in a cascading effect. Not only does equipment shrink in capacity, but ducts, etc. can also downsize, freeing up more room in the house.

Combined with the energy savings over the long run, tight, well insulated construction will turn into a smaller and smaller Δ$ as all the follow-on savings are considered. Plus, Energystar.gov offers subsidized blower-door tests and other means of verification and rebates for good construction practices.

You will also find that the biggest heat gain in most AC conditions are not the walls but the windows. If there is a way to shade them in the summertime and to select the kinds of glass that reject heat gain, you can save a lot of energy. For example, a simple trellis with wysteria or some other diciduous (sic?) plant can keep a area free of sun in the summer (when it would add to the AC bill) and allow sun in during the winter (when solar gain and light are welcome).

Constantin

But Weezbo...

... wasn't the secret to your success re: lowering the heating bills not to heat at all? No wonder your house consumes very little energy! :-)

jerry scharf_2

insulation is a science in itself

As Constantin pointed out, there are several things that make different insulations work different in practice. One is the resistance to temperature flow through the medium. One is the ability of the medium to fill all the voids in the space to be insulated. Another is the amount of thermal bridging from things like studs. Another is the amount of moisture movement through the insulation medium.

Add to this things like fire rating and cost, and there is no perfect insulation.

The pink stuff is the worst, and everyone but the fiberglass people say this. It is very easy to leave voids (my rule of thumbb is a 5% void is a 50% loss in R value.) The air mothion through the medium is so high that it can produce internal convection currents that limit the overall insulation value. The glass won't burn but the binders burn very nicely.

The panel stuff like polyiso is great as long as you foam it into place. Get a closed cell polyurethane foam and foam every edge and penertation to at least 3 inches. Same thing for XPS.

Some people here swear by Icynene, but it's not my favorite foam. I can get much better closed cell foams at just about the same $/sqft/R, at least out this way. My ideal foam also has a low enough perm rating to qualify as a continuous vapour barrier, which is nice for a mixed heating/cooling climate. The trouble is that I know of no foam that meets the specs ans has a 1A fire rating. This means sheet rock or a fire resistant barrier over the whole thing. This almost doubled the insulating cost of one area.

The lowest energy houses are being built with either SIPs or spray foam into I-beam wood studs. I live in shaky country (CA), and SIPs should be geat but are very uncommon. I'm not a general and two people have asked me to general for them on SIP houses they wanted to build. They must be really desperate, given I don't have a GC license!

The load calculators have to derate the insulation for the assumed level of installation carelessness. If you get the insulation right, you should be able to reduce things. But guessing how much is really hard. First you have to decided how good your work will be, and second you have to guess what fudge factor the heal loss porgram included. Then you also need to look at the other losses like windows as well.

I reduced the load on the A/C side by about 25% for my house, and am still fairly sure I'm oversized. I just couldn't bring myself to cut it by 40%, which is what I guess it will be. I'll know in a year.

jerry

Constantin

Very good points!

There is a lot more to insulation than just an R-rating as Jerry points out. Permeability, flammability, friability, etc. are all part of the palette that makes up material qualities.

After our building experience, I am a great fan of Corbond or similar closed-cell polyurethanes. Tough stuff, sticks to anything, excellent perm resistance, very good R-value, fills voids for hours after application, and easy to apply by professionals. The only caveat with such foams is their flammability... Petrified Dino juice comes at a price.

Besides installing blueboard as a code-compliant fire barrier for the Icynene and the Polyurethane, I also retrofit a sprinkler system at $3/ft² to the house, which gives me peace of mind re: the insulation and any pyromaniacal tendencies of any offspring I may produce.

Lastly, take a look over at the research from buildingscience.com where intentionally undersizing a AC system by 20% produced excellent results for comfort and energy bills. It just goes to show that until AC systems can modulate to the same extent as modulating gas burners (i.e. 5-1), that comfort and economy are best achieved by not sizing for the peak load but something lower than that.

I understand that Carrier once had a infinitely-variable scroll compressor but withdrew it after having too many after-sales issues with confused techs butchering units in the field. Evidently, the heating industry isn't the only one that has an education issue.