Summary
Rescheck Slab Insulation Example
Today on the Reschexpert blog we want to look at a Rescheck Example of why slab insulation is so important in the new age Rescheck Softwares of Rescheck Web and Rescheck Desktop. Several years ago a major change happened within Rescheck Web and Rescheck Desktop. The case used to be that you could use less slab insulation that was required by code and increase the insulation values of your roof, windows, doors, and walls. This is no longer the case. If your climate zone requires insulation in your slab you are no longer allowed a tradeoff.
Published by Jobe Leonard from Reschexpert blog and Rescheck.info. Examples and tutorial creation are a hobby of his and sharing them with others is his passion.
Jobe Leonard Rescheck.info
Rescheck Slab Insulation Example
Today on the Reschexpert blog we want to look at a Rescheck Example of why slab insulation is so important in the new age Rescheck Softwares of Rescheck Web and Rescheck Desktop. Several years ago a major change happened within Rescheck Web and Rescheck Desktop. The case used to be that you could use less slab insulation that was required by code and increase the insulation values of your roof, windows, doors, and walls. This is no longer the case. If your climate zone requires insulation in your slab you are no longer allowed a tradeoff. Furthermore, the Rescheck software will automatically fail your project. There are zero opportunities for workarounds or overrides within the software so anytime you are building a new construction, addition, or alteration with a slab it is best to understand the Rescheck slab insulation details before your pour your slab. Insulating a slab to Rescheck standards is inherently more expensive and difficult after the slab is poured. Also a heated slab in Rescheck will require more insulation than a non heated slab. A Rescheck report can help you and your contractor understand these details before it is too late.
Let’s take a look at the project below.
Reschexpert blog reader:
2ENTRY DOORS 36″WIDE
1 FRENCH DOOR 6FT WIDE
6 WINDOWS 36X60
1 WINDOW 36X72
11′ TOP OF WALLS
concrete slab 3.5″ heated with 2.5″ styrofoam board under slab R 5 per inch = 12.5 R Value
Ceiling R38
Walls R13
Rescheck.info:
Running preliminary numbers, this project is lacking some key insulation characteristics for the slab. Based on the R value of the slab Rescheck Web is generating an automatic failure message.
Reschexpert blog reader:
Wow, ok. Is that running IECC 2015 Rescheck criteria?
Rescheck.info:
Yes, I ran the report using the following energy codes just to see if one of them allowed you to build this structure without the slab insulation at the minimum R value of R15 for a heated slab. They are as follows:
IECC 2009 Rescheck Fail
IECC 2012 Rescheck Fail
IECC 2015 Rescheck Fail
IECC 2018 Rescheck Fail
IECC 2021 Rescheck Fail
IECC 2024 Rescheck (this version of Rescheck has not been released yet, but we expect the the requirements to be equally or more stringent and also fail)
Reschexpert blog reader:
So we need to beef up on the ceiling to get as close to r49 as possible?
Rescheck.info:
Mandatory slab insulation on heated slab is r15 in your climate zone. What that means is that no tradeoff is allowed. So increasing insulation in ceiling, walls, windows and doors on this Rescheck is futile. The only true solution to see a Passing Rescheck in this example is to go back and insulate the slab properly according to your Rescheck. Rescheck Web and Rescheck Desktop both create automatic failures in every IECC energy code. The only true solution for this Rescheck is to insulate the slab according to your climate zones mandatory requirements.
Reschexpert blog reader:
Walls are r15 here by code. Do they still need 19?
Rescheck.info
Maybe, you can still use the R15. To even move forward with the Rescheck and a passing Rescheck report you have to clear the hurdle of the missing slab insulation.
Reschexpert Blog User:
What if we do R21 in the walls, and R60 in the ceiling?
Rescheck.info:
Again, the Rescheck softwares of Rescheck Web and Rescheck Desktop create a failing score on this project using all codes. This is because the mandatory slab insulation for a heated slab in Rescheck has not been achieved. No amount or ceiling or wall insulation will move this project to a passing Rescheck score until the slab insulation requirements have been met.
Reschexpert blog reader:
I have priced a set of windows with an extremely low U Value of U.20 and SHGC of .22. Can you input these into Rescheck Web and see if it will help the project pass?
Rescheck.info:
What is the r value of the insulation in the slab?
What is the depth of the slab insulation?
Reschexpert blog reader:
It’s a heated floor and the insulation is 2.5″ at r5/inch or R12.5 total at 4′ depth
Rescheck.info:
R12.5 is below the R15 mandatory minimum for a heated slab. The Rescheck software creates an automatic failure so the project will not pass.
Overall there are some ways to go back to square one and insulate the slab. They are more costly and time consuming that insulating this slab to Rescheck standards to begin with. If you have a slab project that requires a Rescheck you should consult your Rescheck information before you ever pour your slab. Placing the proper insulation before the slab is poured is much easier. Just like the placement of plumbing on a slab you need to have everything in place before the concrete rolls off the truck. If you have a Rescheck that uses a slab and need to know the insulation requirements we can help. It takes about 4-6 hours and we need PDF plans, jobsite address, and square footage.
