HERS Rating 101 – Midpoint Inspections

The HERS Rater’s Function

Utility-sponsored Residential New Construction (RNC) programs in Massachusetts, Connecticut and Rhode Island all require third-party verification before incentives and rebates can be awarded. It’s the role of the HERS rater to perform this function. The Rater acts as a resource for builders and owners, answering questions and providing guidance in order to get the best results. As part of the process, your rater will produce a software-generated model of the home-based on building plans and other input, perform midpoint inspections and final testing and verification at the end of the project. 

Midpoint Inspection

As the name implies a midpoint inspection takes place halfway through the construction process after the insulation is installed but before the sheetrock is hung. Your Rater will verify that program conditions are being met as well as attest to the quality of the insulation installed. Listed below are some of the items a HERS rater looks for during a midpoint:

Cavities behind showers and tubs located on exterior walls must be boarded with a rigid, semi-impervious material such as sheetrock or plywood before the units are installed. It is not uncommon in construction today for subcontractors to install showers and tubs directly onto bare studs. Bathrooms are high moisture areas and moisture can migrate into these unprotected cavities and condense on the inside of the cool exterior sheathing leading to potential mold issues.

Exterior walls behind fireplaces must be boarded for the same reasons described above. 

Attic knee walls must be boarded on the exterior as well as the interior. Although moisture from within the conditioned space is less of a concern, wind wash can be a major issue. Wind wash occurs when outside air pressure causes wind to move through exposed insulation within the knee wall having a cooling effect on the living space within.

Skylight shaft walls must be boarded on the exterior as well as the interior for the same reasons as attic knee walls.

Exterior walls must be insulated to a minimum of R21 according to code. Choice of materials include fiberglass, spray foam, and cellulose, all of which are acceptable and if installed correctly produce great results. Regardless of the type being used, it’s crucial that it’s installed with care to reduce voids, minimize compression and completely fill the cavity. Your Rater will look at this and accordingly assign a grade ranging from one to three. One being excellent and three being poor. The grade system is a tool used to encourage insulation contractors to employ best in industry standards. See pics below:

Stairway walls enclosing stairs leading to unheated basements should be treated like exterior walls although the required R-value can be reduced to R15. 

Floors above unheated basements and garages can be a problematic area. It is very important that the insulation, regardless of type, is in full contact with the underside of the plywood floor above. If a space exists between the underside of the floor and the insulation installed below, cold air will fill this void and may cause the floor to be cold to the touch.

Attic insulation like floor insulation should be installed so that the insulation is in full contact with the ceiling below. If a space exists between the attic insulation and the ceiling being insulated, it will allow cold air to seep in, thus robbing heat from the interior space below.

Hire a HERS Rater

Before starting your next building project contact the Staff at Energy Geeks. From the design stage at the very beginning to the Certificate of Occupancy needed at the very end, we will advise and guide you, thus helping to assure that your next building project will be a success.

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