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Utility Room Space for Solar Thermal Systems

Scope

Include adequate utility room space for a solar hot water storage tank on a floor plan of the utility room when building a Renewable Energy Ready Home (RERH).  Space requirements for solar water heating and photovoltaic system components should be taken into account early in the house design process. 

DOE Zero Energy Ready Home Notes

The U.S. Department of Energy (DOE) Zero Energy Ready Home National Program Requirements includes in Exhibit 1, Mandatory Requirements, Item 7 Renewable Ready, that all homes must meet the requirements in the Consolidated Renewable Energy Ready Home (RERH) Checklist.

The RERH Checklist requires builders to

  • Install and label a 3’ x 3’ x 7’ area in the utility room adjacent to the existing water heater for solar hot water tank.

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. (See the Compliance tabs for additional details and exceptions.)

See the Compliance Tab for related codes and standards requirements, and criteria to meet national programs such as DOE’s Zero Energy Ready Home program, ENERGY STAR Certified Homes, and Indoor airPLUS.

Description

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, the solar hot water storage tank is one of two major components of a solar water heating system that are installed in the utility room. Typically, a domestic hot water solar system with an 80- to 120-gallon storage tank will require approximately 9 square feet of floor space with 7 feet of total vertical clearance. The builder should designate a space no less than 3 ft x 3 ft wide by 7 ft high and locate it near the home’s hot water heater so that any pipe running between the two components can be kept to a minimum. Since the pipe run or pipe chase of the solar hot water system will terminate directly above this space, it should be free of all electrical wiring and service panels as well as windows. Labeling this area as an RERH component is recommended, as is recording its location on a plumbing riser diagram. Once installed, the solar hot water storage tank should become the primary source of hot water, whereas the home’s existing water heater should serve as a backup heating source.

The second major component installed in the utility room is the plywood panel for mounting system components including the pumping package. This panel is described in the guide Mounting Surface for Pumps and Gauges. Additional details on all of the solar water heating system components and requirements can be found in the EPA’s Renewable Energy Ready Home (RERH) Solar Water Heating Specification, Checklist and Guide.

How to Designate Utility Room Space for the Hot Water Tank

  1. To meet the requirements of the DOE Zero Energy Ready Home program, designate a dedicated space for the future solar hot water storage tank, 3 ft wide, 3 ft deep, and 7 ft high. Locate the space adjacent to the home’s hot water heater.
  2. Label the space by placing a 10 in. x 6 in. label or sign on the wall where the water tank will be located that reads “Renewable Energy Ready Home – Future Hot Water Storage Tank.”
  3. Record the tank location on the utility room floor plan to be provided to the homeowner. See Figure 1.
  4. Record the tank location on a plumbing riser diagram.
  5. This dedicated tank space should meet floor load requirements calculated as specified in the guide Adequate Structural Ratings for New Construction.
Utility room 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 pump package mounting panel.

 

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 ensure 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 Energy.gov 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. 

Climate

The DOE Zero Energy Ready Home program’s Consolidated Renewable Energy Ready Home (RERH) Checklist is required only under the following condition related to climate:

-    Location, based on zip code, has at least 5 kWh/m2/day average daily solar radiation based on annual solar insolation using the PV Watts online tool.

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.

Map of average daily solar radiation
Map of average daily solar radiation

Training

Right and Wrong Images

None Available

Presentations

  1. Zero Energy Ready Home Training
    Author(s): Rashkin
    Organization(s): DOE

Videos

None Available

CAD Images

None Available

Compliance

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 (ZERH) Program

The DOE ZERH Consolidated Renewable Energy Ready Home (RERH) Checklist states “Install and label a 3' x 3' x 7' area in the utility room adjacent to the existing water heater for solar hot water tank."

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 these provisions.

Homes that already have a solar hot water system installed do not need to meet the SHW requirements of the Consolidated RERH checklist.

DOE Zero Energy Ready Home National Program Requirements Mandatory Requirement 7 (Renewable Ready) shall be met by any home certified under the DOE Zero Energy Ready Home program, only where all of the following conditions are met:

  1. Location, based on zip code has at least 5 kWh/m2/day average daily solar radiation based on annual solar insolation using PVWatts online tool, AND;
  2. Location does not have significant natural shading (e.g., trees, tall buildings on the south-facing roof, AND;
  3. Home as designed has adequate free roof area within +/-45° of true south as noted in the table below. Note that in some cases a house may have insufficient roof area for the Solar Electric RERH checklist, but it may still have the minimum roof area for the solar thermal RERH Checklist and would therefore have to comply with the Solar Thermal RERH checklist. In other cases, the home may only have adequate south facing roof for the Solar Electric or Solar Thermal RERH Checklist, but not both. In that case the builder can decide which one of those two checklists to apply.
ZERH requirements for south roof area
Table 1. ZERH requirements for south roof area

ENERGY STAR Certified Homes

The ENERGY STAR Certified Homes National Program Requirements for Homes states that “Dwelling units in multifamily buildings with 4 or 5 stories above-grade are eligible to earn the ENERGY STAR if each unit has its own heating, cooling, and hot water systems4, separate from other units, unless the domestic hot water is provided by a solar system.  Then (Footnote 4), “Central systems for domestic hot water are allowed for domestic hot water if solar energy provides at least 50% of the domestic hot water needs for the residential units.”.

2009, 2012, 2015, and 2018 IECC

Section 401.3 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, and 2018 IECC

Section R101.4.3 (Section R501.1.1 in 2015 and 2018 IECC). 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.)

2009, 2012, 2015, and 2018 IRC

M2301 Solar Energy Systems (Solar Thermal Energy Systems in 2015 and 2018 IRC)  - See requirements for solar water heating systems.

Retrofit: 2009, 2012, 2015, and 2018 IRC

Section N1101.3 (Section N1107.1.1 in 2015 and 2018 IRC). 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.)

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

2009, 2012, 2015, and 2018 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 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

  1. Author(s): PNNL, ORNL
    Organization(s): PNNL, ORNL
    Publication Date: December, 2010

    Case study about a 20-unit community of energy-efficient duplexes in Massachusetts that incorporated solar water heating and photovoltaics.

References and Resources*

  1. Author(s): Department of Energy
    Organization(s): DOE
    Publication Date: June, 2012

    Website with consumer and contractor information about building codes and regulations for solar water heating systems.

  2. Author(s): Department of Energy
    Organization(s): DOE
    Publication Date: April, 2017

    Standard requirements for DOE's Zero Energy Ready Home national program certification.

  3. Author(s): Aldrich
    Organization(s): CARB, Steven Winter Associates, SWA
    Publication Date: March, 2013

    Brochure on specifications for solar thermal systems.

  4. Author(s): FSEC
    Organization(s): FSEC
    Publication Date: July, 2014
    Website with information for consumers about solar thermal systems for homes.
  5. Author(s): U.S. Environmental Protection Agency
    Organization(s): EPA
    Publication Date: May, 2011

    Specifications to assist builders in designing and constructing homes equipped with a set of features that make the installation of solar energy systems after the completion of the home’s construction easier and less expensive.

Contributors to this Guide

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

Last Updated: 07/21/2014