Heat losses from heated slabs are greater than that of unheated slabs because the temperature is warmer. Heated slabs-on-grade will feature hot water pipes or coils embedded within or beneath the slab to provide space heating. Unheated slab-on-grade floor: a slab-on-grade floor that is not a heated slab-on-grade floor. Heated slab-on-grade floor: a slab-on-grade floor with a heating source either within or below it. Let's unpack the issue in the context of ANSI/ASHRAE/IES Standard 90.1 - Energy Standard for Buildings Except Low-Rise Residential Buildings.įirst, the standard defines two classes of slab-on-grade: Slab-on-Grade Insulation Requirements in ASHRAE Standard 90.1 When it does, project teams will often lean on energy codes and standards to settle the issue. Happy reading, and let’s keep it sustainable.The prospect of slab-on-grade insulation can become complicated. There are a growing number of resources out there aiming to help designers detail buildings properly. In summary, the proper use of continuous insulation is all about paying attention to the details. It’s a long read but has a lot of useful information regarding this matter. If you or your client don’t desire to specify proprietary systems, the New York State Energy Research and Development Authority ( NYSERDA) commissioned a testing report that describes a number of other fastening system options for continuous insulation. This system has been engineered to allow up to 3” of continuous insulation to pass behind the girt supports. There are proprietary systems that have been developed to deal with this issue such as the DOW-Knight CI System. In climate zone 5 we are required to have a minimum CI of 7.5, resulting in a CI thickness of about 1 1/2". are not approved for attachment through more than 1” of non-supporting material. There are also proprietary clip systems being marketed to perform this same function.Īnother cause for confusion is the fact that many building claddings such as metal panels, fiber cement board/siding, etc. There are a number of solutions to this issue including welding the angles to standoffs at +/- 4’-0” centers, which allows the CI to be installed behind the angles to minimize the effects of thermal bridging. These steel angles are usually fastened directly to the building structure, providing a significant thermal bridge from the interior of the building to the exterior. For example, masonry veneer wall construction typically employs steel relieving angles and steel lintels at window and door heads. Many designers, contractors, and building officials are still not informed about this important aspect of CI. This is where the big problem lies, and why the industry seems to be so confused. This means that furring strips, clip angles, lintels and other large connection details are excluded from the term “fasteners”. With further research we find that the definition of “fasteners” is meant to include screws, bolts, nails, etc. It is installed on the interior, exterior, or is integral to any opaque surface of the building. So, what exactly is continuous insulation?ĪSHRAE 90.1 defines Continuous Insulation as insulation that is continuous across all structural members without thermal bridges other than fasteners and service openings. When CI is properly installed you get the approximate full R-value of the insulation material. This means that a typical 6” metal stud wall construction with R-19 fiberglass batt insulation actually performs at a dismal R-9. So, besides complying with the building code, why do we need continuous insulation? Thermal bridging through framing components reduces envelope insulation performance by 15-20% in wood frame construction and by 40%-60% in metal frame construction. What’s The Big Deal With Continuous Insulation?Ĭontinuous insulation (CI) has been an energy code requirement since the release of ASHRAE 90.1-2004, but unfortunately is still a bit of a mystery to many designers, contractors, and building officials.
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