Skip to main content

Mounting Surface for Pumps

    Scope Images
    Utility room floor plan showing solar hot water tank

    Include adequate, sturdy wall space within a utility room when building a Renewable Energy Ready Home (RERH). Attach a piece of plywood to the wall for mounting solar water heating equipment including the pump and gauges. Space requirements and layout for solar water heating and photovoltaic system components should be taken into account early in the design process. 

    See the Compliance Tab for related codes and standards requirements, and criteria to meet national programs such as DOE’s Zero Energy Ready Home programENERGY STAR Single-Family New Homes, and Indoor airPLUS.


    A renewable energy-ready home (RERH) is one that is built with the wiring and plumbing conduit and other components in place to facilitate the future installation of solar photovoltaic panels and/or solar water heating panels. Some energy-efficiency programs, like the U.S. Department of Energy’s DOE Zero Energy Ready Home Program, require homes to be renewable-energy ready.

    When constructing a home to be renewable energy ready, space should be allocated in the utility room for solar water heating components, including a solar hot water tank and associated components. To meet the requirements of the DOE Zero Energy Ready Home program, dedicate space on the utility room wall for mounting the balance of system components.  A plywood panel at least 3 ft x 2 ft should be fastened to the wall and clearly labeled as the “Balance of System Board.” This panel should be labeled on the plumbing riser diagram as an RERH component.

    The purpose of the plywood backing is to

    • Ensure a dedicated space for these components.
    • Provide a secure foundation for mounting future equipment.
    • Facilitate the future installation of these components by the installer.

    How to Designate Utility Room Space for the Balance of System Board

    1. To meet the requirements of the DOE Zero Energy Ready Home program, designate a dedicated space for the future balance of system components, 3 ft tall by 2 ft wide. Locate the wall space adjacent to the empty space dedicated to the home’s future solar hot water heater.
    2. Label the space by placing a water resistant 10 in. x 6 in. label or sign in the center of the plywood that reads “Renewable Energy Ready Home - Solar Thermal Balance of System Board.”
    3. Record the balance of system wall location on the utility room floor plan to be provided to the homeowner. See Figure 1.
    4. Record the balance of system wall location on a plumbing riser diagram.
    Utility room floor plan.
    Figure 1. The utility room floor plan should include the location of the existing hot water heater, designated space for a future hot water storage tank, electrical outlet, and balance of system plywood panel.


    The Balance-of-System (BOS) components include all of the electrical, mechanical and hardware elements integrated into the solar hot water system.  Some of those elements include: pumps, valves, and the differential controller.  Many of the BOS components need to be protected from the weather elements.  The parts that are required to be installed in weather-resistant enclosure require proper working and maintenance clearances.  As this guide describes, a secure mounting space is required for those components as well.


    In many types of solar hot water installations, a pump is required to circulate water from the storage tank to the solar array on the roof.

    Gauges and Valves

    Pressure gauges and relief valves help maintain the proper water pressure in the system.  If the water pressure ever exceeds a certain limit, the relief valve allows pressure to escape the closed loop, ensuring system pipes remain intact.

    Differential Controller

    This control mechanism compares the temperature between the storage tank and the solar collector.  If the solar collector is hotter than the storage tank by a certain amount, the controller turns on the circulation pump. 

    Ensuring Success

    Ensure adequate utility room early in the house design process to allow for ample space for solar water heating and photovoltaic system components. 

    Confirm with local code officials early in the design process what steps are needed to guarantee that installation of solar water heating panels will meet with local codes, homeowner's association covenants, and historic district regulations. See the article on building codes and regulations related to solar water heating systems at for additional information.

    Protect the electrical and mechanical components of the solar water heating system from bulk moisture, high temperatures and direct sunlight.  The utility room should be properly ventilated and maintain average indoor temperatures. 


    The DOE Zero Energy Ready Home PV-Ready Checklist (Revision 07)  is required only under the following condition related to climate (See the Compliance Tab for other exceptions):

    • Location, based on zip code, has at least 5 kWh/m2/day average daily solar radiation based on annual solar insolation using the PVWatts online tool. See map below. 

    In climates where freezing temperatures are likely to occur, a closed-loop anti-freeze system with heat exchanger will keep outdoor water pipes from bursting.

    Average daily solar radiation per month.
    Figure 1. Map of average daily solar radiation per month (Source: Best Practices Series, Volume 6, High Performance Home Technologies: Solar Thermal and Photovoltaic Systems 2007). 




    The Compliance tab contains both program and code information. Code language is excerpted and summarized below. For exact code language, refer to the applicable code, which may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.


    DOE Zero Energy Ready Home (Revision 07)

    Exhibit 1 Mandatory Requirements.
    Exhibit 1, Item 1) Certified under the ENERGY STAR Qualified Homes Program or the ENERGY STAR Multifamily New Construction Program.
    Exhibit 1, Item 7) Renewable Ready: All homes must meet the requirements in the Consolidated Renewable Energy Ready Home (RERH) Checklist.

    The RERH Checklist requires builders to:

    • Dedicate and label a 3 ft x 2 ft plywood panel area adjacent to empty space (for the solar hot water tank) for the balance of system components/pumping package.

    Alternative: Blocking is permitted to be used as an alternative to the 3’ x 2’ wood panel area designated for the future panel to mount solar HW components shall be clearly noted in the system documentation.

    Note: Homes equipped with an ENERGY STAR qualified whole-home gas tankless water heater or an ENERGY STAR qualified heat pump water heater are exempt from this provision.

    DOE recommends but does not require solar thermal water systems. See the DOE Zero Energy Ready Home Solar Hot Water-Ready Checklist (Encouraged)


    2009, 2012, 2015, 2018, and 2021 International Energy Conservation Code (IECC)

    Section R401.3 A permanent certificate shall be posted on or near the electrical distribution panel that lists types and efficiencies of water heating, heating, and cooling equipment, as well as insulation R values, and window U and SHGC factors.

    Retrofit:  2009, 2012, 2015, 2018,  and 2021 IECC

    Section R101.4.3 (in 2009 and 2012). Additions, alterations, renovations, or repairs shall conform to the provisions of this code, without requiring the unaltered portions of the existing building to comply with this code. (See code for additional requirements and exceptions.)

    Chapter 5 (in 2015, 2018, 2021). The provisions of this chapter shall control the alteration, repair, addition, and change of occupancy of existing buildings and structures.


    2009, 2012, 2015, 2018, and 2021 International Residential Code (IRC)

    Follow the requirements for solar water heating systems found in IRC Section M2301 Solar Energy Systems (Solar Thermal Energy Systems in 2015, 2018, and 2021 IRC).

    Retrofit:  2009, 2012, 2015, 2018,  and 2021 IRC

    Section R102.7.1 Additions, alterations, or repairs. Additions, alterations, renovations, or repairs shall conform to the provisions of this code, without requiring the unaltered portions of the existing building to comply with the requirements of this code, unless otherwise stated. (See code for additional requirements and exceptions.)

    Appendix J regulates the repair, renovation, alteration, and reconstruction of existing buildings and is intended to encourage their continued safe use.


    2009, 2012, 2015, 2018, and 2021 International Mechanical Code (IMC)

    Follow the requirements for solar water heating systems found in the IMC, Chapter 14, Solar Systems (Solar Thermal Systems in 2018 and 2021 IMC).


    More Info.

    Access to some references may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.

    Case Studies
    References and Resources*
    U.S. Environmental Protection Agency
    Publication Date
    The RERH specifications and checklists take a builder and a project design team through the steps of assessing a home’s solar resource potential and defining the minimum structural and system components needed to support a solar energy system.
    Publication Date
    Website with information for consumers about solar thermal systems for homes.
    Aldrich Robb
    Consortium for Advanced Residential Buildings,
    Steven Winter Associates,
    Publication Date
    Brochure on specifications for solar thermal systems.
    U.S. Department of Energy
    Publication Date
    Website listing implementation timelines and links to various versions of the DOE Zero Energy Ready Home national program requirements.
    *For non-dated media, such as websites, the date listed is the date accessed.
    Contributors to this Guide

    The following authors and organizations contributed to the content in this Guide.

    Building Science Measures
    Building Science-to-Sales Translator

    Solar DHW Ready Home =

    Technical Description

    Solar hot water systems use energy from the sun to heat water for use in the home. The easiest time to prepare a home for the installation of these systems is during design and construction. A solar hot water-ready home does this by providing plumbing lines from the attic to the hot water heater, chases for wiring, documentation that the roof is designed to support the extra weight of the solar thermal panels, adequate roof space for the solar collector array that is not shaded, and adequate space in the utility room for an additional solar hot water tank, pumps, and controls. 

    Sales Message
    Last Updated

    Mobile Field Kit

    The Building America Field Kit allows you to save items to your profile for review or use on-site.

    Sign Up  or  Log In

    Did you find this information helpful?

    If you have questions and/or would like a reply to this feedback, please include your e-mail address in the message.
    This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.