SIPs, are an advanced, modern method of Timber Frame construction,
offering far superior insulation, structural strength and air-tightness
than traditional systems
Insulated structural joints and connections combined with the exacting panel tolerances make SIPS one of the easier ways to achieve low levels of air leakage - as low as 0.6 m³/m²hr@ 50 pascals air pressure as standard.
Adequate ventilation is critical to a healthy living environment. The air-tightness of a properly installed SIP system is so much better than traditionally constructed buildings that serious attention should be paid to ventilation methods. Healthy buildings usually require at least 0.5 air changes per hour (m³/m²hr).
The average family of four produces up to 18 litres of water vapour everyday through normal activities such as bathing, cooking, and even breathing. Excess water vapour condenses on the fabric of the building, creating an environment where mould and dust mites can flourish.
Indoor air can be up to ten times more polluted than outside air. An adequate ventilation system must be able to rid the building of indoor air pollutants (cigarette smoke, carbon monoxide, solvent vapours) while keeping out external air pollutants (traffic fumes, pollen, noise). Uncontrolled ventilation (e.g. window trickle vents) can compromise the energy efficiency of a building. The solution is a controlled ventilation system.
Mechanical ventilation with heat recovery (MVHR) offers the best solution to providing adequate ventilation for a SIP house. MVHR Systems are designed to operate 24 hours a day, continuously circulating fresh air through the structure while removing unwanted moisture and pollutants. In a typical application, moist stale air is extracted from wet rooms (kitchens, bathrooms, utility rooms). The air passes through a high efficiency heat exchanger which extracts the heat from the stale air and transfers it to incoming fresh air. Then the pre-warmed drier fresh air is delivered to other rooms. Most heat exchanger systems can recover up to 90% of the heat in the outgoing air, saving energy and money on heating costs. A summer bypass can be installed for when heating the incoming air is not desirable and some units offer integral filters to remove pollen and other particulates from the incoming air.
MVHR systems, in combination with the excellent insulating properties of a SIP house, can greatly improve the energy efficiency of the structure. For more information on the benefits and features of MVHR systems and the optimum size required for your building, contact ADM Systems.
Passive stack ventilation (PSV) systems channel warm moist air up through ducts to an outlet vent in the roof without a fan. The air is typically replaced through natural air leakage through cracks in the building structure or through wall or window vents. Since a SIP building has greater air-tightness than other building types, these inlet vents often must remain permanently open, risking over-ventilation and compromising the energy efficiency of the structure. Since heat recovery is not an option, the incoming air will be the same temperature and humidity as the outside air. The PSV system also can create negative pressure inside the structure, which prevents most fireplaces and stoves from venting properly.
Positive Input Ventilation (PIV) systems use a fan to blow fresh air into the house, pressurizing the building so that moist stale air is forced out through cracks, doors, and windows. In very airtight buildings, additional extract vents may have to be installed. As with PSV, these vents often must remain permanently open, compromising the energy efficiency of the structure. Some PIV systems are able to gather some heat from the roof space to temper the incoming air, reducing the running costs.
Single room or multi-room extractor fans simply blow moist air out of wet rooms, allowing heat to escape. These extractor fans often do not have the power to ventilate an entire house and provide no ability to recover heat or filter incoming air, reducing the energy efficiency of the structure.
Additional information regarding ventilation performance requirements can be found within the Approved Document F of the Building Regulations – Means of Ventilation.