Low Energy House - What is Super Insulation?
Super insulation significantly reduces the transfer of heat through the walls, roof and ground floor of a house. Special attention must be given to the elimination of thermal cold bridges, particularly where walls meet roof, foundations and intersecting walls
Super insulation is an approach to house design and construction that evolved in North America in the 1970s. The principles of super insulation were developed to make timber framed houses more thermally efficient. Timber framed houses are of lightweight construction and therefore rapidly heat up and cool down.
Traditionally, timber framed houses were insulated with mineral wool or cellulose insulation. To increase the performance of the insulation it was usual to construct thicker timber framed walls so that increased thicknesses of insulation could be fitted.
This concept is still valid but, as additional layers of insulation are added, the law of diminishing returns operates until, at some point, one of the additional layers does not constitute value for money.
Today there is a good selection of insulation types to choose from and some, particularly rigid urethane and rigid phenolic boards with reflective facings, can be tightly packed into the timber structure and will achieve very good thermal values
Super Insulation in New Houses
To achieve super insulation in new houses the practical solution is to use a combination of high or medium thermal value insulating material with slightly thicker walls. Manufacturers will provide free U-value calculations for alternative thicknesses of material.
Super Insulation - Timber Frame Construction
In new construction, the cost of any extra insulation and wall framing should be offset by the elimination of a conventional central heating system. With the increasing need for energy efficiency, even deeper studs are being specified.
The most common option is to increase the depth of the studs, from the usual 140mm to 200mm deep, to allow more insulation to be incorporated. For sections deeper than 200mm the use of solid timber is unlikely to be uneconomical. For very thick walls, double stud or planted timber batten systems may be more economical than a composite section.
Super Insulated House Design typically includes:
- High value thermal insulation in the roof, walls and ground floor
- Continuously insulated building envelope with no cold bridges
- Airtight construction, especially at doors and windows
- Triple Glazed Windows
- A Mechanical Heat Recovery Ventilation System
- A minimal back-up heating system
Triple Glazing Windows
Energy efficient, high performance, windows offer excellent thermal performance in
a house that is heated by a conventional heating system.
In the case of super insulated houses the
windows are thermally the weakest point in the building envelope. To overcome this problem it is
advisable to improve on double glazing and to install triple glazed high performance windows with
Low E glass and inert gas fill.
Airtightness of Super Insulation
In a super insulated house, the building envelope must be made airtight with robust detailing, in order to keep the heat loss to a minimum and to maintain comfortable air temperatures. Careful sealing of every construction joint around doors and windows and at all service penetrations is particularly important.
Super Insulation and Mechanical Heat Recovery Ventilation
In a super insulated house, heat loss through ventilation can become a serious problem. Mechanical heat recovery ventilation systems with a heat recovery rate of over 80 per cent are employed to maintain air quality and to recover sufficient heat to reduce, or dispense with, a conventional central heating system.
Super Insulation and Heating from Intrinsic Heat Sources
A super insulated house is intended to be heated predominantly from intrinsic heat sources using heat gains from the body heat of the occupants, solar heat gain, lighting, domestic appliances and other electrical equipment.
Super Insulation and Building Regulations
Building Regulations require external walls to have thermal performance levels by way of insulation and airtightness. Durability of the timber frame is an essential requirement, as walls need to provide support for the cladding materials.
External walls are required to have appropriate fire resistance and internal spread of flame characteristics. In addition, Housing Warranty and Guarantee Authorities have specific requirements for aspects such as sheathing materials, breather membranes and the preservative treatment of external wall framing.
Thermal Values of Super Insulation
The advantages of super insulation should be achieved when the overall fabric U-value is below 0.2 W/m²K.
The performance of an insulating material relies on the amount of air trapped within
it. If that air is kept dry and still then less heat can get into or past the material and the higher
its insulating capacity will be
About Super Insulation - Airtightness - Home Insulation