Air pressure n50 test
The n50-value over one hour is used by the Passivhaus standard to describe the number of air changes that occur within a building's envelope at a pressure difference of 50 Pascals (Pa). The Passivhaus standard is based on a building physics principle that a building can be heated only by the occupants' activities and solar gains. As such the standard is primarily interested in the volume of air that needs to be heated and thus the rate at which that volume of air would be replenished through uncontrolled ventilation or minimised through air tightness.
This is measured through an n50 pressure test which is carried out by closing and sealing doors and windows and installing a door blower to create a pressure differential of 50 Pa (equivalent to a 5 mm water column) between the inside and outside to measure the air change rate. The standard (or n50) requires a test result which is less than 0.6 air changes per hour @ 50 Pascals expressed as < 0.6h-1@50pa. Note that the volume of the building is based on the sum volume of all individual rooms rather than the total volume within the envelope.
[edit] Related articles on Designing Buildings
- Accredited construction details ACDs.
- Air change rates.
- Air permeability testing.
- Air tightness in buildings
- Airtightness of energy efficient buildings.
- Draughts in buildings.
- Energy audit.
- Floor plenum airtightness.
- Indoor air quality.
- Indoor air velocity.
- Passivhaus.
- Site inspections.
- Thermographic survey.
- The history of non-domestic air tightness testing.
Featured articles and news
Retrofit 25 – What's Stopping Us?
Exhibition Opens at The Building Centre.
Types of work to existing buildings
A simple circular economy wiki breakdown with further links.
A threat to the creativity that makes London special.
How can digital twins boost profitability within construction?
The smart construction dashboard, as-built data and site changes forming an accurate digital twin.
Unlocking surplus public defence land and more to speed up the delivery of housing.
The Planning and Infrastructure Bill
An outline of the bill with a mix of reactions on potential impacts from IHBC, CIEEM, CIC, ACE and EIC.
Farnborough College Unveils its Half-house for Sustainable Construction Training.
Spring Statement 2025 with reactions from industry
Confirming previously announced funding, and welfare changes amid adjusted growth forecast.
Scottish Government responds to Grenfell report
As fund for unsafe cladding assessments is launched.
CLC and BSR process map for HRB approvals
One of the initial outputs of their weekly BSR meetings.
Architects Academy at an insulation manufacturing facility
Programme of technical engagement for aspiring designers.
Building Safety Levy technical consultation response
Details of the planned levy now due in 2026.
Great British Energy install solar on school and NHS sites
200 schools and 200 NHS sites to get solar systems, as first project of the newly formed government initiative.
600 million for 60,000 more skilled construction workers
Announced by Treasury ahead of the Spring Statement.
The restoration of the novelist’s birthplace in Eastwood.
Life Critical Fire Safety External Wall System LCFS EWS
Breaking down what is meant by this now often used term.
PAC report on the Remediation of Dangerous Cladding
Recommendations on workforce, transparency, support, insurance, funding, fraud and mismanagement.
New towns, expanded settlements and housing delivery
Modular inquiry asks if new towns and expanded settlements are an effective means of delivering housing.