In order to achieve net-zero energy, all building components must be optimized. This includes insulation.
High R-Values for the wall, roof, and floor resist heat flow, reducing heating energy use and maintaining a comfortable indoor environment.
Installed through government schemes, these measures are expected to save energy across the UK by 2035. However, installation rates have fallen in recent years.
Building Envelope
The building envelope is the primary boundary between indoor and outdoor environments. It includes the air barrier, thermal barrier and weather barrier and offers resistance to soil gases, outdoor temperatures, sunlight, noise, moisture and rain.
A well-insulated building envelope can dramatically reduce energy usage, resulting in significant savings. This is because insulation limits heat transfer between the walls, roof and foundation – which requires less active heating and cooling to maintain an indoor temperature. The effectiveness of insulation is measured by its R-value, which varies depending on the material used. The higher the R-value, the greater its insulating power.
In addition to limiting the flow of heat, insulation can also provide acoustic and fire protection and limit condensation and mold. Choosing the right type and thickness of insulation is essential to achieve these multiple functions.
While a net-zero energy building must incorporate a number of other technologies to reach this goal, a properly functioning building envelope is the foundation for an effective and efficient net-zero home. By implementing good insulation, high-performance windows and adequate sealing around penetrations, such as doors, windows and vents, net-zero energy buildings are able to maximize the benefits of passive design strategies while controlling energy consumption and minimizing environmental impacts.
Walls
In net-zero energy buildings, insulation is key for minimizing heat loss and keeping indoor air temperatures stable. The use of advanced insulation and more energy efficient HVAC systems can reduce overall energy consumption while maximizing comfort for building occupants. Renewable energy generation systems, such as solar photovoltaic panels and solar thermal systems can also offset some of the energy requirements of net-zero buildings.
The insulation used in net-zero homes varies by climate zone, but R-values typically range from R-19 in milder zones to up to R-60 in colder regions. Cellulose insulation is a popular choice for net zero home construction, and it is environmentally friendly and highly resistant to fire, moisture, and pests. Another popular option is ICF, which offers high performance and durability.
While fiberglass and cellulose insulation are a good choice for most new construction, some projects may have design or on-site limitations that prevent the full range of energy efficiency measures from being implemented. In these cases, closed-cell spray foam can be a cost-effective solution to achieve the desired insulation R-values. In addition, spray foam is impermeable to water vapor and provides better air sealing than fiberglass or cellulose, which can make it an excellent choice for unvented attics and crawl spaces.
A well-insulated and air sealed building envelope can significantly reduce energy costs for the life of a commercial or residential structure. To help minimize waste, select the best insulation materials for your project, and install HRVs or ERVs to increase ventilation efficiency and reduce air leakage.
Roof
In net-zero buildings, high-efficiency heating and air conditioning systems work with passive design strategies like natural ventilation and shading to control energy consumption. Insulation is a key component of these passive technologies to enhance thermal performance.
As the primary heat barrier in a home, the roof requires significant insulation to limit heat transfer and reduce cooling demands. Net zero builders often use a combination of insulation materials, including closed-cell spray foam, polyiso board, and plywood. These products combine to create a highly-tight building envelope that reduces active heating and cooling and allows geothermal systems and heat pumps to operate at peak efficiency.
Rigid foam insulation is also a popular choice for the exterior of net-zero homes. It helps prevent the heat from escaping through the walls and into the attic, which can make homes significantly more energy efficient.
A key goal of net-zero construction is to eliminate a large amount of energy waste. Energy is expensive, so eliminating wasted energy saves money for the homeowner and reduces carbon emissions. In new buildings, this can be achieved by incorporating insulation to reduce the heating and cooling loads, and by installing smart building automation and energy-efficient appliances.
In existing buildings, increasing insulation can reduce energy consumption by 25 to 45 percent. In addition to reducing the heating and cooling load, it will minimize energy use for lighting, ventilation, and air conditioning.
Floors
Achieving a net zero energy building requires significant investment in insulation. The UK government is working to meet its climate change targets, which include a target to reduce carbon emissions from buildings to net zero by 2050. Insulation decreases heat loss from walls, roofs and floors, which means less energy is required to warm the home. However, the insulation installation rates in the UK have fallen since 2012. The House of Commons Business, Energy and Industrial Strategy Committee has suggested that more measures be implemented to encourage ‘able to pay’ householders to invest in energy efficiency improvements.
Insulation is also important for the basement and foundations of the building. This prevents ground heat loss, as well as condensation and moisture infiltration from soil. A vapor barrier is often installed to protect the foundations from moisture.
When selecting an insulation solution for a net-zero building, consider the benefits of low carbon and recycled materials. ROCKWOOL stone wool insulation has a lower embodied energy than fiberglass or cellulose. In addition, its low-carbon blowing agent is a better choice for greenhouse gas reduction compared to conventional hydrofluoroolefin (HFO) blowing agents.
Other strategies used in net zero energy buildings include the use of solar panels, geothermal systems, wind turbines and other green energy sources. These systems work in conjunction with high-performance insulation and efficient lighting and HVAC systems to minimize energy consumption and offset the need for fossil fuels.