Commercial Air Pressure / Air Tightness Testing

Many commercial buildings require an air pressure test to ensure fire safety.

• Air pressure tests can be used to increase energy efficiency of existing buildings
• Air leakage testing helps identify areas of a building experiencing heat loss.
• Air leakage testing helps minimise energy usage in a building.
• Air leakage testing plays a vital role in achieving an "A" rated cert building

We offer a streamlined route to achieving air tightness compliance. We work with short lead and response times, transparent pricing structures and provide a tailored service to meet your needs. We have developed a number of additional support services that are designed to assist you at every stage of the air tightness testing process.

What preparation needs to take place in advance of testing?

We provide a simple checklist for building preparation, which includes the following:

• The building should be 'completed'
• All external doors and windows closed
• All internal doors wedged open
• All fire dampers, ventilation louvres and trickle vents closed but not sealed
• Mechanical ventilation turned off with inlet/outlet grilles sealed
• All combustion appliances switched off Drainage traps must contain water

Building type	Air permeability in m3/ (h.m2) at 50Pa
	Normal practice	Best practice
Offices
Naturally ventilated	7	3
Mixed-mode	5	2.5
Air-conditioned	5	2
Factories and warehouses	6	2
Superstores	5	1
Schools	9	3
Hospitals	9	5
Musuems and archival storage	1.5	1
Cold stores	0.3	0.2
Dwellings
Naturally ventilated	9	3
Mechanically ventilated	5	3

Sources: ATTMA Technical Specification Standard 1, Measuring Air Permeability of Building Envelopes. July 2007

What does air tightness testing involve?

The objective is to measure the volume of conditioned air escaping through the building envelope via uncontrolled ventilation at an induced pressure difference of 50Pa.

The following basic steps are typical:

• Check site preparation / Prepare site - including temporary sealing
• Calculate the envelope area if not done previously
• Explain the process to relevant staff and sub-contractors working on or near the building
• Take environmental condition measurements - wind speed, temperatures, barometric pressures
• Install template(s) into suitable aperture(s)
• Install fan(s) into template(s)
• Connect monitoring equipment
• Check the static pressure
• Take multiple pressure difference readings and record fan flow rate(s) - allowing sufficient time for the pressure readings to stabilise
• Check the static pressure
• Process the readings through appropriate software - check that readings fulfil the requirements of the standard
• If the building fails, attempt to identify/quantify air leakage/infiltration paths
• Disconnect measurement equipment
• Remove the fan(s)
• Remove the template(s)

Pre-test assistance:

• Office-based technical advisers
• Design detail evaluation
• Pre-test inspection
• Indicative testing, of components and/or sections of the building
• Identification of test programme (where required) and discussion with Building Control as necessary
• Liaison with site directly
• Envelope area calculations
• Preparation of the building (where agreed in advance)

Post-test assistance:

• Results available immediately,
• Diagnosis - identification of failure points, ideally on the day with the opportunity to resolve issues and repeat the test (where possible)
• Smoke pens
• Depressurisation
• Smoke testing

Air Tightness Testing FAQs

Typical examples of air leakage paths

• Seal hollow concrete beams at the ends before delivery to site since internal penetrations of the beams would allow air to pass into the cavity.
• Seal profiles in profiled metal sheeting - for ceiling where concrete is poured on to profiled metal sheeting, the underside will have indents in the profile. These should be sealed with mastic or similar.
• Check blockwork leakage. Plastered blockwork does not leak and so quality of blockwork is immaterial. However, where there are raised floors and suspended ceilings, the quality of blockwork is important if these areas are not plastered. Blockwork may leak by up to 60m3/(h.m2). And the manufacturers should have data on the air leakage of the blockwork. Painting good quality blockwork reduces the air leakage but painting poor quality blockwork has very little effect.
• Seal joints of profiled metal decking. The underside of profiled metal decking roofs is the air tight membrane. All joints will require to be effectively sealed during the laying of the sheets. Perforated liner sheets and using the vapour barrier should be avoided since they usually underperform.
• Effectively seal all walls to ceiling and roof joints.
• Fill all expansion joints between concrete beams and blockwork to blockwork with an airtight compound.
• Drylining systems should be sealed to the floor, roof and walls and all service penetrations sealed. Care should be exercised where internal walls meet those external walls to avoid a lattice of air leakage paths.
• Seal joints of curtain walling systems to other building systems where problems are most likely to occur.
• Seal riser shafts effectively to avoid air penetrating the cavity and or plant rooms.
• Seal windows and door frames effectively to the inside surface of the structure and seal the cavity preferably before the final finishes are carried out.
• Seal steelwork penetrations through the inside surface of the structure adequately.
• Seal pipework and electrical penetrations through the building envelope including penetrations to the plant room, electrical switch rooms, external lighting systems, and power and communications in to the building.
• Provide adequate seals for lift shaft doors below raised floors to prevent air penetrating the lift shaft.
• Check doors and shutters. Loading bay doors should preferably be of the panel type with adequate seals. Security shutters are not particularly good from an airtightness point of view.
• Fill water traps and condensate traps before testing the structure.
• Take extra care with sealing details for renewables, such as light pipes through to roofing sheets, mounting, pipe and cables penetrations for solar water heating and photovoltaic's. Even mounts and cables for wind generators mounted on roofs of buildings should be carefully sealed.
• Do not use unfaced mineral wool or equivalent to fill gaps.
• Do not use tape to seal joints in buildings.
• Avoid the use of expanding foam.

Floor Void and Ceiling Void Testing

Floor Void

Raised floor voids used for the supply of ventilation air must be constructed to high levels of airtightness to eliminate losses of air to other parts of the building and to outside.

Typically, sub-floor only tests are performed by mounting a fan on the walked on floor to measure the total leakage of the below floor space. That is the holes below the floor and the holes through the walked on floor. The walked on floor is usually so leaky that this test fails.

The next step is to then measure the below floor leaks that the agent would actually escape from. Essentially, we want to measure the size of the "drain hole" below the floor since this hole size determines the loss rate. This is done by neutralizing the flow across the walked on floor with a fan mounted in the door to the room or covering the floor with plastic.

Ceiling Void Testing

This method employs a flex duct to connect the second fan to the above ceiling space. If the above ceiling space has less than 9 square feet of leaks this second fan will pressurise above the suspended ceiling while the first fan is measuring the lower leaks. To ensure that the lower fan is measuring only the lower leaks, the fans are balanced using smoke across the ceiling. A ceiling tile is lifted, and then smoke is puffed in the crack to see if air is being drawn past the suspended ceiling by an imbalance in pressures between the above and below ceiling spaces. Adjustments are made with the smoke as a guide to ensure the lower fan is making an accurate measurement of the lower leaks. The smoke is usually very sensitive and will detect an imbalance of a few cfm that would be impossible to measure any other way. Lack of smoke movement shows that air from above the suspended ceiling is not leaking past it to yield a false reading on the lower fan. The upper fan does not measure anything - it just acts to balance the pressure across the ceiling.

Flynn's Energy Ratings offer full technical support in preparation for the tests and can advise on typical areas of failure and the necessary approach during floor /Ceiling and services installation to successfully achieve the specified airtightness performance.

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