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Frequently Asked Questions

Air Tightness

What is Air Tightness?

Air tightness tests have a variety of names. Air permeability, air infiltration and air leakage tests are all exactly the same as an air tightness test. (more information)

Air tightness is a measure of how much air leaks out of a dwelling per hour, per metre cubed of building envelope – m3.hr/m2

What is a building envelope?

A ‘building envelope’ is the floor area, walls area and roof area all added together – as if the building were wrapped in an envelope.

These are all the areas where air could potentially leak out of a building

Why do I need an Air Tightness Test?

  1. To check for air leakage out of the building
  2. To make sure you’re not too air tight
  3. To comply with building regulations

How is a test conducted?

We put a large fan in an expandable door frame, which goes into an external door in the house, normally the front door. All other external doors and windows will be closed and all internal doors kept open.

The fan will then typically depressurise the house to a pressure of at least -50Pa. An anemometer reads the internal pressure, external pressure and the strength that the fan is having to work at to create that pressure difference.

10 readings are taken at different pressures, and along with other factors such as barometric pressure and temperature, fed into a software which calculates the air leakage.

What is a DAP?

DAP stands for Design Air Permeability. It is the target score for the air test, determined in the SAP Calculations or Code for Sustainable Homes (CSH) conditions.

It is the amount of air leakage allowed for a particular property in order to gain building control sign-off. The building regulations state that a score of 10m3.hr/m2 is sufficient for a pass, but increasingly target scores determined in SAPs are far lower than that, around 5m3.hr/m2

At what stage do I need an air test?

Testing is typically performed post second fix. All major penetration to walls and floors must have already been made. On top of this, you’ll need:

  • All service penetrations sealed
  • Trickle vents installed
  • Loft access hatch in place
  • Plumbing complete with water in the traps
  • Seals fitted on external doors
  • Electrical outlets fitted

Does every plot need an air test?

Not always, but increasingly that is becoming the case. Sample testing is only allowed if the plots you do test beat their target score by 2m3.hr/m2. This means, if your DAP is 10, but you can score 8 on the plots you do test, you may not need to test every plot – however this is still at the discretion of building control.

With more and more low target scores, the likelihood of beating it by 2 is less and less likely.

How do I make sure I pass?

While we will never guarantee a pass, we will do as much as we can to help you.

Before we come, take a look at the diagram on our air tightness testing page. It highlights common air leakage areas in a property. If you address all of these, you give yourself a good chance.

If a test is not passing first time, we will help you out as much as we can within a fair time frame. If you ensure you have tubes of mastic and expanding foam with you on the day, our engineers can point out air leakage areas during the testing. If they are small enough to fix at the time, we’ll wait and re-test the property, doing our best to get you a pass first time.

Is it only new builds that need an air test?

Short answer… yes.

However, we would argue that it is a good idea to get any house that has not already got an air test certificate tested for air tightness. It’s a great way to locate air leakage areas, plug them up and save yourself money on heating. It’s also far more cost effective than other methods, such as thermographic surveys.

What qualifications do RJ Acoustics have?

All air tightness engineers for RJ Acoustics have been trained on an ATTMA approved course. We would never allow any of our engineers to complete air tests without being fully qualified to do so. You can check our registration status here.

Sound Insulation

What is Sound Insulation Testing?

Sound insulation testing is also known as acoustic testing, and is a measure of sound transfer between party walls and floors in buildings. The type that RJ Acoustics provides is generally between walls and floors of domestic dwellings, although we also test between commercial units.

Two types of sound are measured – airbone and impact.

Why do I need a Sound Insulation Test?

Building Regulations Part E states that all new build or newly converted dwellings must pass a sound test in order to receive a building completion certificate.

The regulations were brought in to allow people living in adjoining properties a decent standard of living, so that only an acceptable level of noise can be heard from their neighbours

How is a test conducted?

Both airborne and impact measurements are recorded during a test. To create airborne sound we use a large speaker, and a microphone and decibel meter measures the amount of sound travelling through the party wall/floor. The sound is intended to mimic other airborne sounds, such as talking, the radio and the television.

Impact sound is created by a Tapping Machine. This is a small box with metal hammers which tap on the floor, creating a similar sound to footsteps, washing machines etc. This is again measured with a microphone and decibel meter on the other side of the floor.

At what stage do I need a Sound Insulation Test?

Ideally, a test should be carried out as early as possible, as problems are more difficult to fix the further along you are. Where possible, it’s recommended that testing is carried out before kitchens or bathrooms are installed.

The minimum that we would need to be able to carry out a test is:

  • All doors, windows and seals should be fully fitted and closable
  • All electrical fittings should be fitted and working
  • 240V mains power must be available on-site in all rooms
  • Gaps in walls and floors should be fully sealed
  • All walls and ceilings should be plastered
  • There should be no holes remaining in floors or ceilings
  • Testers will require access to all rooms on all levels

Does every plot need testing?

No. Sound testing is always completed as sample testing, thus one set of tests is required for up to 10 dwellings i.e. 2-10 dwellings will need one set of tests, but 11 will need two sets of tests.

Additional testing is also required where more than one type of construction has been used on walls or floors.

Who decides which plots to test?

The testing body (us) will select at random which plots to test. Sometimes building control will request certain plots, but generally it is up to the tester.

How do I make sure I pass?

Speak to us! We have consulted on hundreds of building projects in the past (see our testimonials), and can guarantee a pass as long as the work is carried out exactly as we specify in an on-site consultation.

If a sound insulation test fails, it can often cost hundreds or even thousands of pounds to rectify, so it really is worth speaking to us at the early stage of a build, to ensure peace of mind.

What Qualifications Do You Have?

The Building Regulations Part E Section 0.4 says that the testing body should be UKAS accredited, or a member of the ANC (Acoustic Noise Consultants) is acceptable. RJ Acoustics are UKAS accredited for sound testing, and our lead acoustic consultant has completed over 5000 sets of tests in his 10 year career – you won’t find many more experienced sound testers in the country.

Ventilation

What is Ventilation Testing & Commissioning?

Ventilation testing and ventilation commissioning are actually two different things. ‘Testing’ refers to extractor fans, like you would find in a toilet, bathroom or kitchen. These are tested to see how much air they extract.

‘Commissioning’ refers to more complicated ventilation systems, such as Mechanical Ventilation Heat Recovery (MVHR). These need to be balanced, to make sure the correct amount of air is either being extracted from or supplied to every room in the house.

Why do I need a Ventilation Testing and Commissioning?

Building Regulations Part F state that all new builds now need their ventilation tested and/or commissioned. If a house does not have sufficient ventilation, it can cause major problems with mould, damp and condensation. A lot of people aren’t aware for example that trickle ventilators on windows are designed to be left open all the time, no matter what the temperature is outside.

Even if your house isn’t a new build, if you experience any of the above issues, we would recommend getting your extractor fans tested.  We have found that many extractor fans don’t pull even nearly enough air out of a room. This is sometimes due to the extractors themselves but often also due to long and convoluted duct runs, adding pressure and inhibiting extraction.

What are the different types of ventilation system?

There are 4 different types recognised in building regulations part F:

  • Type 1 – Intermittent extract fans with background ventilators

This is what is found in most houses – Extractor fans in kitchens, toilets and bathrooms and trickle ventilators on the windows.

  • Type 2 – Passive Stack Ventilation

This is very rarely seen. It is a system which uses a combination of cross ventilation, buoyancy (warm air rising) and the venturi effect to ventilate. It is rarely used because it’s very much weather dependant.

  • Type 3 – Mechanical Extract Ventilation (MEV)

This can either be a whole house system or a localise system for specific rooms. Multiple ducts will run from a constantly running unit to wet rooms (kitchen, WC, bathroom) continuously extracting stale air. When these rooms are in use, the system will boost up to extract a larger volume of air

 

  • Type 4 – Mechanical Ventilation Heat Recovery (MVHR)

This is similar to Type 3, except that it also supplies fresh air to all non-wet rooms (bedrooms, dining room, living room). The heat from the stale extracted air is kept in the central unit and used to heat the fresh air from outside before it is supplied to the house.

How is a test conducted?

For Type 1, we use an anemometer (wind speed meter) to test the amount of air each extractor is extracting.

Type 2 is not tested

For types 3 and 4, we use the same anemometer, but we can open and close vents, and turn the central units up and down until each vent is supplying or extracting the correct volume of air, as specified in Part F

At what stage do I need a ventilation test?

Generally, at the end of a build. Once your extractors are in, working and connected up to duct runs. We also need all windows and doors to be fitted and ‘closeable.’

Does every plot need testing?

Yes. The regulations came in in 2010, but we are still noticing that many building control officers aren’t asking for the test before giving sign-off. They should be, and it’s always a good idea to get every plot tested anyway.

How do I make sure I pass?

To give yourself the best chance of passing, research which fans/units give the best performance. When you have selected your equipment, do your best to keep duct runs as short as possible, with as few twists and turns as possible. Every turn and every inch of ducting creates resistance, reducing the effectiveness of the fan.

We recommend using semi-rigid ducting, as it holds its diameter whilst going through turns, reducing resistance.