Modular Home HERS Rating process

To meet Massachusetts Stretch code it is critical that modular home projects be well organized. Communmication must be good for accurate HERS modeling, to avoid any surprises and issues that may complicate compliance with codes and targeted rebate programs.

For an overview of what a HERS Ratings is, visit this page

Relevant links and downloads referenced on this page:

• PowerHouse Spec Sheet - modular home specifications (pending) - required to begin HERS rating

• Mass Save Terms & Conditions - 2023 - rebate program application

  Energy Star Airbarrier checklist, sections 2 & 4 - required from factory

HERS Rating Process

Steps of a HERS Rating summarized :

1. Plans and specifications are presented by the Client

The building plans, foundation plans, and a Spec Sheet (see below) detailing strategies and systems for HVAC and appliances, are provided for inputs into our HERS energy model. A design review and kickoff meeting is included in our scope to support you with making these decisions.

2. Preliminary HERS Rating is completed - energy model based on plans and the provided specifications

All energy related features are inputted into our HERS energy model: insulation, windows, HVAC, appliances, lighting, air leakage etc. To complete this we need a completed Specification Sheet . Suitable defaults can be entered for unknown features, as long as we are on the same page. A Preliminary HERS Certificate is presented to the client based on this model. The modular home factory and the town building commissioner will require a passing Preliminary HERS Certificate (score of 52 or lower) to issue a Building Permit and for the factory to begin construction.

3. Construction starts, the factory documents insulation and air-sealing

4. Photos of under slab, and slab-edge insulation are required from the site build team. Photos of any insulation installed on site and not visible at the Final Inspection, are also required. The factory must provide photos showing the installed insulation type and completeness. The required airbarrier checklists are completed by the factory (see below)

If there are changes to the provided specifications, the client or site builder must update the HERS Rater with changes to confirm the project is still on track for code compliance, and to meet any established energy performance targets (above code rebates etc)

4. Midpoint inspection may be required

If significant insulation is installed on site, we may need to complete a Midpoint HERS Inspection. Note that this is typically not included in our base scope.

5. Final HERS Inspection

When the home is complete (plumbing done water in traps, heating/cooling operational, ventilation running continuously, envelope ready for a blower door test) a Final HERS Inspection is conducted. This includes blower door, duct leakage, and ventilation system testing, which must meet IECC Code Mandatory performance testing thresholds. The HERS Rater must be notified at least one week before the inspection is requested.

Any issues identified at the final inspection are communicated immediately.

6. Final HERS Certificate is provided / rebates submitted

Based on the final built conditions, we complete the HERS Rating and provide you with a Certificate to provide to the building official and to provide to the Owner of the home. Upon payment of the final invoice, rebates are submitted to the utility program to be issued to the determined recipient.

Pre Construction Specifications - Required, so we can start modeling

To complete the Preliminary HERS Rating, we need to understand how the home is going to be built : we need to know the specifications for all the insulation , mechanical equipment , and appliances. We can use suitable defaults if specific equipment has not been selected yet. However, understanding the strategy (system types) is important.

As modular homes require coordination between multiple stakeholders to result in a succesful end product, we ask our client to coordinate between the various parties and with us the required specifications using this form.

To begin our modeling, we need this simple ‘spec sheet’ completed.

• Preliminary HERS Rating spec sheet
  [add example image to lighbox]

If specifications are unclear , please reach out to us for recommendations. We offer a design review meeting as part of our scope, to help you make decisions to ensure code compliance and good energy performance. Below here , we offer recommended energy related specifications to meet the current MA 2021 IECC Stretch code requirements.

2021 IECC Stretch Code Guidelines - <52 HERS strategies

We can provide recommendations for building specifications to meet the 2021 IECC Stretch Code required HERS rating (<52 HERS gas heat, <55 HERS heatpumps - until June 30, 2024) . Please see this blog post for an overview of recommended specifications for a code compliant home.

Factory Required Documentation - verification of factory built assemblies

To give full credit for insulation values, we need some photo documentation from the factory, showing insulation type and quality of install for all insulation not visible at our Final HERS Inspection.

An airbarrier checklist is required as well, for factory sealed assemblies - attic flat, wall etc. The Mass Save rebate program requires the Energy Star checklist linked to below be completed - the factory must complete their relevant sections. If not pursuing Mass Save rebates, then equivalent airbarrier checklists are acceptable, pending review. This factory checklist must be signed by a credentialed individual, not necessarily a HERS rater.

• Example of factory photos showing detailed airsealing and cavity insulation [link to Dropbox gallery]

• Energy Star Airbarrier checklist - sections 2 & 4

Mass Save Rebates