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Undersized Heating System with DHP & HRV at Far Reach Home

Case Study by Nathaniel Kinne
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Undersized Heating System with DHP & HRV at Far Reach Home
Heating, Ventilation & AC
Heating and Cooling
Ductless Heat Pump
Thurston County
Rowland Zoller, Thurston County
Matt Cooper and Eileen Ryan
Scott Homes, Inc.
Scott Homes, Inc.
5 Star Built Green EERE’s Builders Challenge (HERS 39) rating Energy Star certified EPA Indoor airPLUS Qualified Home Silver EVHA Award


This home’s exterior envelope was constructed entirely from SIPs, and the interior was heated with a Ductless Heat Pump and included a Heat Recovery Ventilator for indoor air quality, all resulting in an extremely airtight, energy efficient non-standard home. While no building codes were ignored, the home incorporates several systems many building officials may be unfamiliar with.

Permitting Process

This technology was permitted as a part of the home’s larger, airtight design. This home is constructed from Structural Insulated Panels and only requires 7800 BTU to heat, however the smallest DHP available produces 21000 BTU. Thanks to much education, the building official was willing to permit this technology, understanding that despite challenging the code, this solution was the most efficient for the home’s overall design.

Project Description

Matt Cooper and Eileen Ryan wanted to build the most cost effective energy efficient home they could, so they turned to Scott Bergford of Scott Homes, Inc. Scott Homes has built with Structural Insulated Panels for 18 years and is very familiar with their level of performance. However, the company had never used the panels in the entire envelope. Scott struck a deal with the Matt and Eileen where, if he could experiment by building their house entirely with SIPs, including floor, walls, and roof, he would absorb the extra cost of the thicker SIPs. Washington State University Extension Energy Program was brought in to study the project and record the performance of the house. WSU studied the engineering of the residence and ran various heating options through their modeling programs. A Ductless Heat Pump was chosen to heat this home because it heats efficiently while minimizing heat loss through the building envelope to the outside. DHPs are extremely effective in airtight homes, and use fewer resources than traditional means of heating. They also filter the conditioned air, improving indoor air quality.

The Heat Recovery Ventilator is used in conjunction with the DHP to filter incoming air and use the air’s energy to preheat incoming air. This further lowers the amount of energy used to heat the home and also improves indoor air quality. The Building Official needed documentation showing that this technology would cover the home’s heat load requirements, and in fact it can cover nearly triple the load. The official signed off due to the extensive education provided by the builder, engineer and WSU’smodeling.

The home’s envelope is comprised entirely of SIPs, making the whole house conditioned space, including the attic spaces. When a blower door test was administered, the results showed .65 ACH50, or .65 Air Changes/Hour at 50 Pascals, a result just above the industry’s most airtight method of construction, the Passiv Haus. To meet Passiv Haus standards, a structure must show .6 or less ACH50, meaning the Far Reach House is not far off. The residents are very pleased with the finished home as it is extremely airtight and very cozy. According to the residents the average daily operating cost is $3.20. Electricity used for heating has shown to be lessened by simple activities like cooking or having guests over, both of which naturally heat the home.

The house has been rated 5 Star Built Green, it meets EERE’s Builders Challenge (HERS 39) rating, is Energy Star certified, is an EPA Indoor airPLUS Qualified Home, and will be receiving either the Silver or Gold EVHA award in Feb 2012

Approval Requirements

Heat Load Calculations were required before a permit could be issued. Because the plans called for only one heater, the Permitting Official had to submit due diligence to ensure the health and well-being of the occupants.

Project Contacts
Owner: Eileen Ryan Builder: Scott Bergford Scott Homes (360) 357-9167 Designer: Peter Bergford Scott Homes (360) 357-9167
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