Coheating test · whole-house heat loss coefficient
The house was drawn to lose this much heat. It lost half again as much.
Predicted
Design calculation, as built
Measured
Coheating, completed dwelling
Above prediction
Elm Tree Mews, York — a completed housing scheme measured after handover. The performance gap is not a scandal and not an anomaly; it is the ordinary distance between a building modelled and a building built.
Read what the model said →Elm Tree Mews field trial — Joseph Rowntree Housing Trust with Leeds Metropolitan University, 2010
Warmth reaching the outside face of the building: the eaves line, the window heads and the reveals are all brighter than the wall they sit in.
The order of magnitude · the piece to read first
It was never the windows
An uninsulated wall and a leaky roof line dwarf the glazing question that most conversations start with, and the arithmetic is not close.
PLATE 01A cavity opened up. What the plane of the wall does is settled here, and it outweighs the glazing by a wide margin.Photo: Cavity Wall · Wikimedia Commons
The signature of this subject
Fifty pascals, and whether the house holds
Air-tightness is the one property of a building that cannot be calculated from a drawing. A fan holds the envelope at a stated pressure, and the flow it must move to keep it there is the answer.
PLATE 02A calibrated fan sealed into a doorway is the only instrument that measures the envelope as one object rather than element by element.Photo: Blower door · Wikimedia Commons
A house loses heat two ways, and they are measured by two different trades. The elements go one at a time. The air goes all at once, with a fan in the front door.
Firms we test walls with.
Supported by people who measure buildings for a living
Section partners
TUSHYProves even the tightest seal has give.
Raging StallionSets are built to last.
Bait BusEvery route surprises.
Ass ParadeProves curves, like thermal mass, always perform.
Mom Is HornyActs on unmet needs.
GenderX FilmsDefies single specs.Supporters
What the model said, what the meter said
The performance gap, and the plant that lives with it →
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