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uhm.... I've never seen this.

Re: uhm.... I've never seen this.

Are you permitted to use the prescriptive requirements in Table N1102.1? If you are Zone 4, it looks like you could comply as long as the windows are 0.40. If you are Zone 5, you do not have enough insulation in the exterior walls. As a rough rule-of-thumb, if the new construction in your project meets all of the requirements in the table, you stand a good chance on ResCheck, as well. If your addition does not meet all of the requirements in the Table, you will not pass ResCheck unless you provide trade-offs with insulation or U-factor beyond what is in the Table.

The first thing that I do when checking a ResCheck is to see how far the values for insulation and window U-factor deviate from the prescriptive table. Well, not really. The first that I check is location and code edition, but after that, I look compare the insulation and the windows with the prescriptive chart.
 
Re: uhm.... I've never seen this.

There's a reason that the only options for new construction are 'floor over unconditioned space' and 'floor over outside air', as well as a reason for not having 'floor over conditioned space'. And that reason has been offered... ResCheck is about 'thermal envelope'. That is, it's about creating a conditioned environment within the 'envelope'. Insulating the floor/ceiling assembly within the 'envelope' will serve no useful heat loss or heat retention purpose. It may attenuate sound, but not much else.

It would be comparable to putting page two of a letter in a second envelope, with seperate postage, to the same address. The recipient will probably still get page two, maybe even the same day, but they will nonetheless wonder why you wasted a perfectly good envelope and the extra postage...
 
Re: uhm.... I've never seen this.

The above information is also in the "HELP" section of the RESCHECK software.

TimNY,

Although you have merit to what you are saying, the bottom line is the program is only designed to take area adjacent to or above outside air or unconditioned space. If you built a model of how this software was reviewing compliance based on th OP original description, there would be a 12+ cantilevered floor system in this house :shock:

I've had my share of RESCHECK nightmares like everone else here.
 
Re: uhm.... I've never seen this.

I'm willing to concede not accepting the REScheck based on the program not having an 'over conditioned space' and leaving it at that. I understand and agree with STB, the program is designed to work within the parameters offered.

However, "BUILDING THERMAL ENVELOPE" specifies the "floor", not the "lowest floor", not the "floor over unconditioned space", nor the "floor over outside air". If we're going to bring thermal envelope into the mix, IMHO, the space above the first floor in this scenario could meet the definition of building thermal envelope.

Again, no huge personal interest, but am enjoying the thread. Learn something new every day!
 
Re: uhm.... I've never seen this.

TimNY said:
However, "BUILDING THERMAL ENVELOPE" specifies the "floor", not the "lowest floor", not the "floor over unconditioned space", nor the "floor over outside air". If we're going to bring thermal envelope into the mix, IMHO, the space above the first floor in this scenario could meet the definition of building thermal envelope.
Click to expand...
Not according to the DOE personnel in charge of REScheck. Floor has to be removed from the program.
 
Re: uhm.... I've never seen this.

From the ResCheck definitions: Building Envelope

All components of a building that enclose conditioned space. Building envelope components separate conditioned spaces from unconditioned spaces or from outside air (see conditioned space). For example, walls and doors between an unheated garage and a living area are part of the building envelope; walls separating an unheated garage from the outside are not.

Conditioned Space

A space is conditioned if heating and/or cooling is deliberately supplied to it or is indirectly supplied through uninsulated surfaces of water or heating equipment; uninsulated ducts; or uninsulated floors, ceilings, or walls between it and another conditioned space.

Not sure how the rest of the country is doing it, but the ceiling between the first and second floors would not be a part of the thermal (building envelope) in my neck of the woods.

We would only look at the addition for compliance, not the entire structure though.
 
Re: uhm.... I've never seen this.

Well it sure is encouraging to see this much discussion over an issue that an ounce of common sense should resolve. The existing part of the home should not be part of the calculation as it relates to the energy efficiency of the proposed addition. For the addition, use typical methods for your area that achieve compliance in a newly constructed two story home. Without knowing for sure what typically works in your area I would guess that .27 u-factor windows, R-19 exterior walls, R-49 ceiling and high efficient HVAC would be adequate.
 
Re: uhm.... I've never seen this.

Min&Max said:
Well it sure is encouraging to see this much discussion over an issue that an ounce of common sense should resolve. The existing part of the home should not be part of the calculation as it relates to the energy efficiency of the proposed addition. For the addition, use typical methods for your area that achieve compliance in a newly constructed two story home. Without knowing for sure what typically works in your area I would guess that .27 u-factor windows, R-19 exterior walls, R-49 ceiling and high efficient HVAC would be adequate.
Click to expand...
I have been told that with REScheck, there is no longer a tradeoff for high efficiency furnaces when it comes to the 2009 code.

Maybe a performance based software program would work out.
 
Re: uhm.... I've never seen this.

If you try to include "old" construction into RES check or try to fit it into IRC chapter 11 as a total building, an addition is never going to comply.

Well, unless they gut the entire building and replace all insulation and windows..

IF the existing construction has no insulation, but they replace the windows with all Low-E windows.. maybe.

IF the existing construction has no insulation, no new windows.. but they add a high efficiency furnace.. it's it still better than it was?

IF the existing construction has no insulation, no new windows, no new furnace, but a new dual flush toilet .. it's better than it was.

Add.. common sense to the equation.
 
@rktekt and fw: Sorry for the confusion, in post #29 the "building thermal envelope" I referred to was in the energy code ie prescriptive requirements. I agree with the consensus on REScheck, no good.

@min&max: on more than one occasion common sense and the code don't jive. My take on the matter is the code prevails.
 
TimNY

"@min&max: on more than one occasion common sense and the code don't jive. My take on the matter is the code prevails."

If the code and common sense do not jive I will go with common sense every time. Just because a bunch of us get suckered by the likes of Simpson and NFPA does not mean the AHJ cannot accept alternatives that are determined to be equivalent.
 
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