Home Innovation Insights

Going beyond HVAC - how to keep homes cool and efficient

Katie Dorn
August 28, 2023

5 NGBS Practices to Beat the Summer Heat

The summer of 2023 has marked the hottest temperatures on record in human history. In order to stay cool, many households have their air conditioners running at full blast, resulting in high energy bills. Whether you are building a new home or retrofitting an existing one, the NGBS has several innovative practices that can be used to minimize heat gain. Check out these five practices in the ICC 700- 2020 National Green Building Standard that can help keep your home cool and reduce energy bills.

1. Roof Surfaces

Solar Reflectance Index (SRI) is a value that measures how much solar heat roofing materials absorb. SRI is calculated using solar reflectance and thermal emittance and produces a value from 0 to 100, with 100 being the most solar heat gain. Homes and buildings can earn three points for practice 602.2 Roof Surfaces if at least 90% of the roof’s surface is constructed of the following:

  • products that are in accordance with the ENERGY STAR® cool roof certification or equivalent 
  • a vegetated roof system (along with a high SRI, vegetative roof systems also reduce the surface temperature of roofs)
  • minimum initial SRI of 78 for low-sloped roof and a minimum initial SRI of 29 for a steep-sloped roof 

2. Heat Island Mitigation

A Heat Island is an urbanized area with a lack of green space and a large amount of dark colored, impervious surfaces causing the air and surface temperature in that area to be significantly warmer than the surrounding rural areas. Under practice 505.2 of the NGBS, projects can earn 10 points total for having the site designed to mitigate the heat island effect. For this practice, five points can be earned if 50% or more of the hardscape surface area uses the following: 

  • Shade is provided from existing or new vegetation or from trellises
  • Light-colored horizontal hardscaping materials are installed with an SRI of 29 or greater
  • Permeable hardscaping materials are installed

Projects can earn an additional five points if 75% or more of the exposed surface of the roof is vegetated. The vegetation must be capable of withstanding the climate conditions of the jurisdiction.

3. Exterior Doors

In order to protect homes and buildings from the effects of solar radiation and precipitation, practice 602.1.10 awards two points (six points max) for each exterior door that has a porch roof or awning installed, an extended roof overhang, a recessed exterior door, or a storm door installed. Awnings, porch roofs, and roof overhangs can significantly reduce solar heat gain through exterior doors by blocking direct sunlight. Additionally, since awning and overhangs are not on an enclosed space, the heat is not transferred inside.

4. Passive Cooling Design

Practice 703.7.3 Passive Cooling Design awards up to six points maximum for installing features into the design of the home that naturally reduce heat gain. By reducing heat gain, these features help manage the temperature of the home without using any additional energy source. Point-earning features include:

  • Exterior shading on east and west windows 
  • Overhangs installed on south-facing glazing 
  • Windows and/or venting skylights that facilitate cross and stack effect ventilation
  • Solar reflective roof or radiant barrier installed (climate zones 1, 2, or 3)
  • Minimum thickness of 3 in. for internal exposed thermal mass (concrete, brick, and/or tile fully adhered to a masonry base or other masonry material)
  • Roofing material has a minimum continuous air space of 0.75 in., offset from the roof deck from eave to ridge

5. Energy Recovery Ventilator

Homes and buildings can earn eight points for having an energy-recovery ventilator under 902.2.1 (4).  Energy recovery ventilators supply fresh outdoor air into the home and remove stale indoor air from the home or building while capturing the humidity from the air to keep it on the same side of the thermal envelope. During the summer, the ERV removes the humidity from the outside air before it enters the home. This reduces energy consumption and costs by reducing the loads on air conditioners and dehumidifiers.

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