Superinsulation is an approach to building design, construction, and retrofitting that dramatically reduces heat loss (and gain) by using much higher insulation levels and airtightness than average. Superinsulation is one of the ancestors of the passive house approach.
There is no universally agreed definition of superinsulation, but superinsulated buildings typically include:
Nisson & Dutt (1985) suggest that a house might be described as "superinsulated" if the cost of space heating is lower than that of water heating. [1]
Besides the meaning mentioned above of high level of insulation, the terms superinsulation and superinsulating materials are in use for high R/inch insulation materials like vacuum insulation panels (VIPs) and aerogel. [2]
A superinsulated house is intended to reduce heating needs significantly and may even be heated predominantly by intrinsic heat sources (waste heat generated by appliances and the body heat of the occupants) with small amounts of backup heat. This has been demonstrated to work even in frigid climates but requires close attention to construction details in addition to the insulation (see IEA Solar Heating & Cooling Implementing Agreement Task 13).
The term "superinsulation" was coined by Wayne Schick at the University of Illinois Urbana–Champaign. In 1976 he was part of a team that developed a design called the "Lo-Cal" house, using computer simulations based on the climate of Madison, Wisconsin. Several houses, duplexes and condominiums based on Lo-Cal principles were built in Champaign–Urbana in the 1970s. [3] [4]
In 1977 the "Saskatchewan House" [5] was built in Regina, Saskatchewan, by a group of Canadian government agencies. It was the first house to demonstrate the value of superinsulation publicly and generated much attention. It originally included some experimental evacuated-tube solar panels, but they were not needed and were later removed. The house was heated primarily by waste heat from appliances and the occupants. [4] [6] In 1977 the "Leger House" was built by Eugene Leger, in East Pepperell, Massachusetts. It had a more conventional appearance than the "Saskatchewan House", and also received extensive publicity. [4] Publicity from the "Saskatchewan House" and the "Leger House" influenced other builders, and many superinsulated houses were built over the next few years. These houses also influenced Wolfgang Feist's development of the Passivhaus standard. [4]
It is possible, and increasingly desirable, to retrofit superinsulation to existing houses or buildings. The easiest way is often to add layers of continuous rigid exterior insulation, [7] and sometimes by building new exterior walls that allow more space for insulation. A vapor barrier can be installed outside the original framing but may not be needed. An improved continuous air barrier is almost always worth adding, as older homes tend to be drafty, and such an air barrier can be significant for energy savings and durability. Care should be exercised when adding a vapor barrier as it can reduce drying of incidental moisture or even cause summer (in climates with humid summers) interstitial condensation and consequent mold and mildew. This may cause health problems for the occupants and may damage the structure. Many builders in northern Canada use a simple 1/3 to 2/3 approach, placing the vapor barrier no further out than 1/3 of the R-value of the insulated portion of the wall. This method is generally valid for interior walls with little or no vapor resistance (e.g., they use fibrous insulation) and controls air leakage condensation and vapor diffusion condensation. This approach will ensure that condensation does not occur on or to the inside of the vapor barrier during cold weather. The 1/3:2/3 rule will ensure that the vapor barrier temperature will not fall below the dew point temperature of the interior air and will minimize the possibility of cold-weather condensation problems.
For example, with an internal room temperature of 20 °C (68 °F), the vapor barrier will then only reach 7.3 °C (45 °F) when the outside temperature is at −18 °C (−1 °F). Indoor air dew point temperatures are more likely to be in the order of around 0 °C (32 °F) when it is that cold outdoors, much lower than the predicted vapor barrier temperature, and hence the 1/3:2/3 rule is quite conservative. For climates that do not often experience −18 °C, the 1/3:2/3 rule should be amended to 40:60 or 50:50. As the interior air dewpoint temperature is an important basis for such rules, buildings with high interior humidities during cold weather (e.g., museums, swimming pools, humidified or poorly ventilated airtight homes) may require different rules, as can buildings with drier interior environments (e.g., highly ventilated buildings and warehouses). The 2009 International Residential Code embodies more sophisticated rules to guide the choice of insulation on the exterior of new homes, which can be applied when retrofitting older homes.
A vapor-permeable building wrap on the outside of the original wall helps keep the wind out and allows the wall assembly to dry to the exterior. Asphalt felt and other products, such as porous polymer-based products, are available for this purpose and usually double as the water-resistant barrier/drainage plane.
Interior retrofits are possible where the owner wants to preserve the old exterior siding or where setback requirements limit space for an exterior retrofit. Sealing the air barrier is more complex, and the thermal insulation continuity is compromised (because of the many partition, floor, and service penetrations); the original wall assembly is rendered colder in cold weather (and hence more prone to condensation and slower to dry), occupants are exposed to significant disruptions, and the house is left with less interior space. Another approach is to use the 1/3 to 2/3 method mentioned above—to install a vapor retarder on the inside of the existing wall (if there is not one already) and add insulation and support structure to the interior. This way, utilities (power, telephone, cable, and plumbing) can be added to the new wall space without penetrating the air barrier. Polyethylene vapor barriers are risky except in frigid climates because they limit the wall's ability to dry to the interior. This approach also limits the amount of interior insulation that can be added to a relatively small amount (e.g., only R-6 insulation can be added to a 2×4 R-12 wall).
In new construction, the extra insulation and wall framing cost may be offset by not requiring a dedicated central heating system. A central furnace is often justified or required to ensure sufficiently uniform temperatures in homes with numerous rooms, more than one floor, air conditioning, or large size. Small furnaces are not very expensive, and some ductwork to every room is generally required to provide ventilation air. When peak demand and annual energy use are low, costly and sophisticated central heating systems are only sometimes needed. Hence, even electric resistance heaters may be used. Electric heaters are typically only used on cold winter nights when the overall demand for electricity in the rest of the house is low. Other backup heaters, such as wood pellets, wood stoves, natural gas boilers, or even furnaces, are widely used. The cost of a superinsulation retrofit should be balanced against the future price of heating fuel (which can be expected to fluctuate from year to year due to supply problems, natural disasters, or geopolitical events), the desire to reduce pollution from heating a building, or the desire to provide exceptional thermal comfort.
During a power failure, a superinsulated house stays warm longer as heat loss is much less than usual, but the thermal storage capacity of the structural materials and contents is the same. Adverse weather may hamper efforts to restore power, leading to weeks or more outages. When deprived of their continuous supply of electricity (either for heat directly or to operate gas-fired furnaces), conventional houses cool rapidly and may be at greater risk of costly damage from freezing water pipes. Residents who use supplemental heating methods without proper care during such episodes or at any other time may subject themselves to the risk of fire or carbon monoxide poisoning.
In passive solar building design, windows, walls, and floors are made to collect, store, reflect, and distribute solar energy, in the form of heat in the winter and reject solar heat in the summer. This is called passive solar design because, unlike active solar heating systems, it does not involve the use of mechanical and electrical devices.
Thermal insulation is the reduction of heat transfer between objects in thermal contact or in range of radiative influence. Thermal insulation can be achieved with specially engineered methods or processes, as well as with suitable object shapes and materials.
In building design, thermal mass is a property of the mass of a building that enables it to store heat and provide inertia against temperature fluctuations. It is sometimes known as the thermal flywheel effect. The thermal mass of heavy structural elements can be designed to work alongside a construction's lighter thermal resistance components to create energy efficient buildings.
In the context of construction, the R-value is a measure of how well a two-dimensional barrier, such as a layer of insulation, a window or a complete wall or ceiling, resists the conductive flow of heat. R-value is the temperature difference per unit of heat flux needed to sustain one unit of heat flux between the warmer surface and colder surface of a barrier under steady-state conditions. The measure is therefore equally relevant for lowering energy bills for heating in the winter, for cooling in the summer, and for general comfort.
A radiant barrier is a type of building material that reflects thermal radiation and reduces heat transfer. Because thermal energy is also transferred by conduction and convection, in addition to radiation, radiant barriers are often supplemented with thermal insulation that slows down heat transfer by conduction or convection.
A low-energy house is characterized by an energy-efficient design and technical features which enable it to provide high living standards and comfort with low energy consumption and carbon emissions. Traditional heating and active cooling systems are absent, or their use is secondary. Low-energy buildings may be viewed as examples of sustainable architecture. Low-energy houses often have active and passive solar building design and components, which reduce the house's energy consumption and minimally impact the resident's lifestyle. Throughout the world, companies and non-profit organizations provide guidelines and issue certifications to guarantee the energy performance of buildings and their processes and materials. Certifications include passive house, BBC—Bâtiment Basse Consommation—Effinergie (France), zero-carbon house (UK), and Minergie (Switzerland).
Passive house is a voluntary standard for energy efficiency in a building, which reduces the building's ecological footprint. It results in ultra-low energy buildings that require little energy for space heating or cooling. A similar standard, MINERGIE-P, is used in Switzerland. The standard is not confined to residential properties; several office buildings, schools, kindergartens and a supermarket have also been constructed to the standard. The design is not an attachment or supplement to architectural design, but a design process that integrates with architectural design. Although it is generally applied to new buildings, it has also been used for refurbishments.
A vapor barrier is any material used for damp proofing, typically a plastic or foil sheet, that resists diffusion of moisture through the wall, floor, ceiling, or roof assemblies of buildings and of packaging to prevent interstitial condensation. Technically, many of these materials are only vapor retarders as they have varying degrees of permeability.
A building envelope or building enclosure is the physical separator between the conditioned and unconditioned environment of a building, including the resistance to air, water, heat, light, and noise transfer.
Renewable heat is an application of renewable energy referring to the generation of heat from renewable sources; for example, feeding radiators with water warmed by focused solar radiation rather than by a fossil fuel boiler. Renewable heat technologies include renewable biofuels, solar heating, geothermal heating, heat pumps and heat exchangers. Insulation is almost always an important factor in how renewable heating is implemented.
Building insulation is material used in a building to reduce the flow of thermal energy. While the majority of insulation in buildings is for thermal purposes, the term also applies to acoustic insulation, fire insulation, and impact insulation. Often an insulation material will be chosen for its ability to perform several of these functions at once.
Building insulation materials are the building materials that form the thermal envelope of a building or otherwise reduce heat transfer.
A thermal bridge, also called a cold bridge, heat bridge, or thermal bypass, is an area or component of an object which has higher thermal conductivity than the surrounding materials, creating a path of least resistance for heat transfer. Thermal bridges result in an overall reduction in thermal resistance of the object. The term is frequently discussed in the context of a building's thermal envelope where thermal bridges result in heat transfer into or out of conditioned space.
A crawl space is an unoccupied, unfinished, narrow space within a building, between the ground and the first floor. The crawl space is so named because there is typically only enough room to crawl rather than stand; anything larger than about 1 to 1.5 metres and beneath the ground floor would tend to be considered a basement.
Cellulose insulation is plant fiber used in wall and roof cavities to insulate, draught proof and reduce noise. Building insulation in general is low-thermal-conductivity material used to reduce building heat loss and gain and reduce noise transmission.
Rigid panel insulation, also referred to as continuous insulation, can be made from foam plastics such as polyurethane (PUR), polyisocyanurate (PIR), and polystyrene, or from fibrous materials such as fiberglass, rock and slag wool. Rigid panel continuous insulation is often used to provide a thermal break in the building envelope, thus reducing thermal bridging.
Insulating glass (IG) consists of two or more glass window panes separated by a space to reduce heat transfer across a part of the building envelope. A window with insulating glass is commonly known as double glazing or a double-paned window, triple glazing or a triple-paned window, or quadruple glazing or a quadruple-paned window, depending upon how many panes of glass are used in its construction.
Dynamic insulation is a form of insulation where cool outside air flowing through the thermal insulation in the envelope of a building will pick up heat from the insulation fibres. Buildings can be designed to exploit this to reduce the transmission heat loss (U-value) and to provide pre-warmed, draft free air to interior spaces. This is known as dynamic insulation since the U-value is no longer constant for a given wall or roof construction but varies with the speed of the air flowing through the insulation. Dynamic insulation is different from breathing walls. The positive aspects of dynamic insulation need to be weighed against the more conventional approach to building design which is to create an airtight envelope and provide appropriate ventilation using either natural ventilation or mechanical ventilation with heat recovery. The air-tight approach to building envelope design, unlike dynamic insulation, results in a building envelope that provides a consistent performance in terms of heat loss and risk of interstitial condensation that is independent of wind speed and direction. Under certain wind conditions a dynamically insulated building can have a higher heat transmission loss than an air-tight building with the same thickness of insulation. Often the air enters at about 15 °C.
Interstitial condensation is a type of condensation that may occur within an enclosed wall, roof or floor cavity structure, which can create dampening.
The Saskatchewan Conservation House is an early exemplar of energy-efficient building construction that introduced best practices for addressing air leakage in houses. It was designed in response to the energy crisis of the 1970s at the request of the Government of Saskatchewan. The Saskatchewan Conservation House pioneered the use of superinsulation and airtightness in passive design and included one of the earliest heat recovery systems. The house did not require a furnace, despite prairie winter temperatures as low as −24 C at night.
