During our daily REScheck reports one of the most common foundations that we see is a slab. Some of the questions we see every day, are ones asking us the correct way to enter a slab component into REScheck. Today we would like to discuss a few basics of the slab foundation as it is used in REScheck.
A slab, in it’s simplest form, was one of the earliest types of foundations. Rock, hardened sand, or compacted earth could all have formed the slab of a home many years ago. Today you are looking at a perimeter of concrete footers buried around the perimeter of the home. With this you will use at least a 4″ of poured concrete. This typically comes complete with vapor barriers and layer of gravel. In some slabs you will even find piping that allows the floor to be heated radiantly.
REScheck treats slabs differently than other types of foundations. Crawl spaces and foundations in REScheck both look at either the square footage of wall area, or the square footage of floor area. Depending on where the foundation’s insulation is placed. However on a slab foundation in REScheck the secret to entering it correctly is to measure around the full perimeter, excluding porches, and enter this calculation into your REScheck report. Basically what you are looking at is the LF of where the wall system meets the actual slab.
One key to realize is that if you just attach your stud wall directly to the slab, with no insulation, your connection will leak energy for the rest of your life. In blower door tests, this is one area that glows red time after time. At the slab and wall system connection I would suggest using at least an R-1 insulation around the perimeter to stem this. You could even go up to an R-4 for just a few dollars more, and save thousands over the life of your home.
Overall using a slab on your structure that needs to be RESchecked can be a great idea. The cost per square foot compared to basement or crawl space is lower, along with the excavation and material requirements. Done correctly this can be one of the greatest most solid foundations you can build. Doing a slab correctly means making it energy efficient and that can be handled in several ways. If you need some help notating your slab correctly in REScheck reporting just let us know. We would be glad to help.
It is also possible you might be wondering about the following related topics like:
How is a Slab entered in Comcheck?
How do I properly calculate a slab for a Manual J?
Does a slab matter for Manual S ACCA equipment sizing?
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