Design

The Kingspan TEK Building System can be considerably more air-tight than conventional constructions, achieving air leakage rates as low as 0.08 air changes per hour at normal pressures.

It is widely accepted that healthy buildings require a minimum air leakage rate of 0.5 air changes per hour at normal pressures. This is typically achieved with conventional construction techniques, but may not be achieved with buildings constructed using the Kingspan TEK Building System when both wall and roof panels are combined. Therefore additional ventilation may be a sensible and beneficial addition to a building constructed with the Kingspan TEK Building System.

The Building Regulations / Standards encourage architects and builders to ‘Build Tight, Ventilate Right’. This means controlled ventilation. Introducing controlled ventilation is considered good practice in energy efficiency terms.

Ventilation Options
One method seems to offer the best solution:

Typical MVHR Unit Design

These systems bring controlled volumes of fresh air into the building and exhaust controlled volumes of moisture laden or stale air to the outside. With the addition of heat recovery, these systems can recover heat from outgoing air to preheat the incoming air. This heat recovery can provide a large proportion of the heat required to keep a building at comfortable living temperatures.

NB: It is the responsibility of the domestic scale mechanical ventilation with heat recovery systems supplier, for the specific sizing of the equipment and the environmental and improved indoor air quality advantages associated with their systems.

The addition of humidity control to the mechanical ventilation system can provide an environment in which dust mites cannot thrive. This may be of benefit to some asthma sufferers.

Another possibility is:

Figure 1 MVHR System

Ducts run from ‘wet’ rooms - kitchens, bathrooms etc. - up to roof terminals. Warm moisture-laden air rises up the ducts as a result the stack effect, requiring no electric fan or power source. These ducts can have humidity controlled vents i.e. they become activated when humidity levels reach a set point.

Wall or window inlets provide a flow of replacement fresh air into the building as required. In order to provide fresh air in living areas these inlets may need to be placed in dry rooms. These inlets could be humidity controlled, but the building will still need ventilation when these rooms have low humidity and therefore closed vents. Humidity controlled inlets would appear to be counter productive in a building constructed with the Kingspan TEK Building System.

The position of inlets and extract ducts ensure that air always moves from ‘dry’ rooms to ‘wet’ rooms, where it is extracted.

Disadvantages - the system may need inlets in ‘dry’ rooms for it to provide adequate ventilation in a very air-tight building. These inlets may have to remain permanently open and thus provide paths for unwanted wind-generated air-leakage. Although desired ventilation could be achieved, there is a risk that undesired over-ventilation could compromise the energy performance of the building through uncontrolled ventilation.

Advantages - while heat recovery is not an option, the system operates with no energy use.

Figure 2 Passive Stack Ventilation System

These systems act rather like mechanical extract in reverse. A fan blows air into a property and effectively pressurises the building. In a building with ‘normal’ levels of air-tightness, this air is forced out through normal air-leakage pathways e.g. cracks, poorly fitting doors and windows etc., taking moisture and air pollutants with it.

In a very air-tight building these pathways may not occur to any useful extent and so extract ventilation ports may have to be provided. As with PSV, the position of inlet ducts and extract ventilation ports ensure that air always moves from ‘ dry’ rooms to ‘wet’ rooms, where it is extracted. These extract ventilation ports could be humidity controlled, but the building will still need ventilation when these ‘wet’ rooms have low humidity and therefore closed vents. Humidity controlled inlets would appear to be counter productive in a building constructed with the Kingspan TEK Building System.

Disadvantages – the system may need extract ventilation ports in ‘wet’ rooms for it to provide adequate ventilation in a very air-tight building. These extract ventilation ports may have to remain permanently open and thus provide paths for unwanted air-leakage. Although desired positive input ventilation could be achieved, there is a risk that undesired wind-generated overventilation could compromise the energy performance of the building. Why ‘Build Tight’ to keep energy use down then cut holes in the system to allow uncontrolled ventilation?

Advantages - while heat recovery is not an option, some systems claim to preheat input air by gathering solar heat from the batten space under roof tiles. This may reduce running costs.

Figure 3 Positive Input Ventilation System