© ProAir Systems: Heat Recovery Ventilation Specialists
Airtightness FAQ's
What is airtightness?
Airtightness is the control of airflow in a building. In an airtight building air leaks do not occur at ceiling or wall junctions, plaster board joints, doors, windows, service entry points etc. Leaks create discomfort and heat is lost. The result is that the heating system has to operate at a greater capacity to compensate for the losses. Airtightness is absolutely essential in maximising the effectiveness of thermal insulation, ensuring vast savings over a lifetime.
Why should air tightness be looked at in the context of HRV installation and operation?
Air tightness is a measure of the flow of air in and out of a building. Improving air tightness in a dwelling can reduce air leakage - the uncontrolled flow of air through gaps and cracks in the fabric of a building. The aim of air tightness is to "build tight, ventilate right". This means that there are no breaks or gaps in the envelope of the building fabric. There is complete control over the ventilation system within the building when using a HRV system. Having an airtight house does not mean there is insufficient air flow, it means that the air flow can be controlled.
Where are the most common air leakage Paths?
Airtightness is the control of airflow in a building. In an airtight building air leaks do not occur at ceiling or wall junctions, plaster board joints, doors, windows, service entry points etc. Leaks create discomfort and heat is lost. The result is that the heating system has to operate at a greater capacity to compensate for the losses. Airtightness is absolutely essential in maximising the effectiveness of thermal insulation, ensuring vast savings over a lifetime.
Why should air tightness be looked at in the context of HRV installation and operation?
Air tightness is a measure of the flow of air in and out of a building. Improving air tightness in a dwelling can reduce air leakage - the uncontrolled flow of air through gaps and cracks in the fabric of a building. The aim of air tightness is to "build tight, ventilate right". This means that there are no breaks or gaps in the envelope of the building fabric. There is complete control over the ventilation system within the building when using a HRV system. Having an airtight house does not mean there is insufficient air flow, it means that the air flow can be controlled.
Where are the most common air leakage Paths?
How should the airtightness of an existing house be approached?
Air tightness testing highlights areas of heat loss. Infiltration of cold air from the outside should be minimised by reducing unintentional air paths as far as is practicable by (i) Fitting draught stripping in the frames of the openable elements of windows, doors and roof lights, etc. (ii) Sealing around loft hatches (iii) Ensuring that boxing for concealed services is sealed at floor and ceiling levels (iv) Sealing piped services where they penetrate or project into hollow constructions, cavities, or voids. (v) Sealing around underfloor ventilator grilles, gaps in and around suspended timber floors, extractor fans, etc. Open chimneys are a major source of air leakage.
What level of airtightness should be achieved so that a HRV system will be beneficial?
The revised Building Regulations will require that houses will need to achieve a result of below 10 m³/hr/m². We suggest that all buildings should attempt to meet the best practice of 3 m³/hr/m². With a level of 5 m³/hr/m² the HRV system will add to comfort levels and reduce heating costs.
Air tightness testing highlights areas of heat loss. Infiltration of cold air from the outside should be minimised by reducing unintentional air paths as far as is practicable by (i) Fitting draught stripping in the frames of the openable elements of windows, doors and roof lights, etc. (ii) Sealing around loft hatches (iii) Ensuring that boxing for concealed services is sealed at floor and ceiling levels (iv) Sealing piped services where they penetrate or project into hollow constructions, cavities, or voids. (v) Sealing around underfloor ventilator grilles, gaps in and around suspended timber floors, extractor fans, etc. Open chimneys are a major source of air leakage.
What level of airtightness should be achieved so that a HRV system will be beneficial?
The revised Building Regulations will require that houses will need to achieve a result of below 10 m³/hr/m². We suggest that all buildings should attempt to meet the best practice of 3 m³/hr/m². With a level of 5 m³/hr/m² the HRV system will add to comfort levels and reduce heating costs.