Blower Door & Airtightness comparisons
Airtightness testing, air-leakage detection and what the numbers actually mean for your home.
Blower door testingBlower Door vs Smoke Testing for Air Leakage
The blower door measures the quantity of air leakage; smoke tracing reveals its location. Smoke testing is almost always carried out during a blower door test, because the pressure difference is what makes the smoke move through the leaks. One gives the number, the other gives the map.
Read comparisonBlower Door Test vs EPC
A blower door test measures the real airtightness of a building; an EPC is a simplified rating that assumes a default air-leakage value rather than measuring it. They are not comparable: the blower door produces hard data used in heat-loss modelling, heat pump sizing and Passive House work, while an EPC gives a broad-brush rating from assumptions. If you want to know how your home actually performs, the EPC will not tell you — the measurement will.
Read comparisonBlower Door Test vs SAP
A blower door test is a measurement; SAP is a compliance calculation. They are not rivals — SAP actually uses an airtightness figure as an input, and that figure is either a pessimistic default or a measured value from a blower door. Feed SAP a real test result and the model improves; rely on the default and the compliance margin shrinks. For accuracy you want the measurement; for Building Regulations you need the SAP calculation.
Read comparisonBlower Door Test vs PHPP
A blower door test is a physical measurement; PHPP is the design model that consumes it. PHPP needs a realistic airtightness value to predict heating demand accurately, and the blower door supplies it — first as a design target, then as a verified result. They are sequential rather than alternative: model in PHPP, build to the airtightness target, then test with the blower door to prove the building matches the model.
Read comparisonAirtightness Testing vs Ventilation Assessment
Airtightness testing measures the uncontrolled air leaking through gaps; a ventilation assessment checks the controlled fresh air the home deliberately provides. The principle is 'build tight, ventilate right': you seal the random leakage and then provide proper, controlled ventilation. Doing one without the other is the classic mistake — sealing a home without ventilation worsens condensation, while ventilating a leaky one wastes energy. You need both, in balance.
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