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Indoor air quality and ventilation service

Ventilation and indoor air quality service


Indoor air quality matters to everyone. Poor indoor air quality effects health and mood too. Excess humidity (water vapour) and high CO2 (Carbon Dioxide) levels can lead to mould growth, condensation, headaches and, they are associated with a range of other health problems.

mould colony due to damp and poor indoor air quality

This extensive mould colony should be removed – but if the cause isn’t identified and rectified, it will be back.

These are quite modern issues, which did not feature in the 20th century, when houses were served by open fires and when draught exclusion, was in its infancy.

Now, in the 21st century, most of the calls we receive, asking for help with damp, are the result of stale and unventilated living conditions.

What can be done to change indoor air quality for the better?

There are a wide range of mechanical ventilation systems available and we understand them all. As the causes of damp have evolved, our expertise has moved with the times too.

Over the past five years we have invested money and time in researching the indoor air quality problem. We’ve talked to manufacturers of advanced ventilation and air purity systems. We’ve attended courses and passed exams in ventilation too. We have two bpec qualified domestic ventilation engineers in house.

This combines with our three decades of experience in dampness in buildings, to create the premier indoor air quality management service in Yorkshire.

Ventilation system manufacturers are the experts on equipment, they make it afterall. However, qualified and experienced specialist surveyors like us, add another extra layer of knowledge. We know buildings and building materials. Together with our ventilation qualifications, these skills ensure that the right equipment is chosen, based on a thorough site evaluation, with evidence based specification of any improvements in ventilation.

Poor indoor air quality causing condensation thermal image

Persistent mould next to a child’s bed – highlighted by our surveyor, seen here as condensation via one of our thermal imaging cameras

Evidence based specification? What’s that?

Where indoor air quality and mould is concerned, there is no such thing as a magic bullet; no ‘one size fits all’ method. It’s not just that all houses are different; two semi-detached houses, adjacent to each other are quite similar. However, people differ; their habits, comfort levels, work patterns, numbers of children, pets and hobbies… the list goes on. There really is no such thing as the average house.

There’s nothing to be gained by recommending improvements of any kind, if the cause of the problem hasn’t been clearly identified first. There must be evidence, which logically supports any chosen intervention – this is one of our guiding values. These values are built into our indoor air quality service, for your benefit. We are not a sales driven company, employing ‘free surveys’ to sell products. Our low survey fee mean you get the right answers.

Read on for more details or, why not speak to a knowledgeable member of our team? Please call us Leeds 265 2752 York 566577 or Sheffield 224 5121 or email us about indoor air quality via our contact page, .

observator unconditional test method

Air flow through an extract fan, precisely measured during ‘Commissioning’ to part F using the unconditional method.

A full diagnostic indoor air quality service

So, first things first; we always carry out a detailed survey of the home.  Its size, number of bedrooms, wet rooms (like bathrooms, kitchens, utilities and such), occupancy levels, construction method and materials, type and heating regime. This is just for starters…

We’ll document the extent of excessive visible mould; check If there is mechanical ventilation, how it is ducted and we’ll test that it is sufficient and performing properly.

Background ventilation is checked too and of course. We’ll also include a full dampness survey, checking for rising damp, penetrating damp and condensation.


indoor air quality tests to unconditional and minimum benchmark level

Our qualified and friendly surveyors offer fan testing using UKAS calibrated equipment

Provided you’re present we’ll also sit and have a chat. We can really find out what is impacting on your enjoyment of the home and together, we’ll agree a way forward.

Sometimes a more forensic approach is needed. We may use thermal imaging, humidity, temperature or CO2 data logging. A range of additional tests are available too. In cases where these are needed we’ll tell you.

A full written report will outline what is happening and specify any ventilation improvements which will deliver the results you need. We can even data log the installation before and after to demonstrate the system meets the design target we’ve agreed if required.

Our surveyors are qualified and we can commission any home ventilation system in accordance with the Building regulations (approved document Part F 2010). Tests include Unconditional and minimum benchmark if needed.


Some of our indoor air quality and mould reduction solutions

System 1 intermittent extract fans:

indoor air quality enhanced by DMEV

Our adaptable, whisper quiet extract fans is guaranteed for 5 years

These are the common type of extract fan most people are familiar with. In effect they are turned on and off by the user, though sometimes a light switch or infra-red detector may be used. They need to operate at a high air flow rate because they are not on all the time. This means they tend to be quite noisy. As a result, they tend to be less efficient, simply because people tend to use them only when a real need arises.

The advanced System 1 fans we use are ultra-quiet and economic to run. They do have a place in modern homes, though we tend to favour System 3 continuous extraction in many cases.


System 3 – Continuous extract fans


These come in de-centralise and centralised form. They are ‘on’ all of the time, though at a very low setting, which offers great 24/7 air changes.

centralised extract via a system 3

Where multi room extract is required, a centralised extract system in the loft is a great option.

They also have a boost function, which can be automatically or manually switched for those times where a need occurs, such as when cooking up a pan of stew, or when showering. In effect system 3 ventilation acts almost like an old fireplace may have done, in days past; allowing air to escape, but in a controlled way. The home stays fresh and airy, without the draft on the back of the neck, associated with a solid fuel fire.


System 4 – Continuous extract ventilation, with heat recovery.

When air is extracted from a kitchen or bathroom, replacement air is sucked into a house from outside. This air may be cold and will need heating up in winter.

System 4 equipment solves this problem of heat loss, by supplying air via additional ducting. An advanced heat exchange unit is used. The heat being drawn out of the house is recovered here and is carried back into the home, with the clean dryer air from outside.

heat recovery for great indoor air quality

Our Single Room Ventilator with heat recovery mode is a revolution in indoor air quality

These systems are costlier to install, as there is twice as much ducting and the units are more expensive. However, much of the cost is recovered in saved energy, which would otherwise be wasted.

They also supply filtered air, rather than air simply dragged into homes via windows and trickle vents, so where asthma or hay fever sufferers are concerned, they hit the spot.


Whole House Ventilation systems.


We supply, install and commission a number of these innovative systems. These include Positive Input Ventilation (PIV) units and Single Room alternate-flow extract units with heat retention (SRVHR).

We carefully match the correct unit to the home size, layout and occupancy to achieve the required number of air changes per hour (ACH). Research has shown that at least 0.5ACH are needed to maintain good indoor air quality. This is almost never achieved in modern air-tight homes, without retro-fitting additional equipment.

The air these units’ supply is pre-filtered to remove pollen and other particulates. Usually the air is drawn from the loft space. They really do have a huge positive effect on indoor air quality. The air can be pre-heated, however, this is rarely needed. This is because on average the air in a loft space is a few degrees higher than the air outside. In addition, the air is diffused horizontally at ceiling level, so it mixes freely with warm air, which tends to nestle at ceiling height. Fresh air from outside is lower in CO2 and contains less water vapour too. This is why PIV’s are often used to reduce mould growth caused by condensation.


Banish mould and condensation. Breath fresh, clean and dry air throughout the home

PIV’s are not a cure-all, though sometimes they are marketed as such (by those who sell them of course). They will not reduce condensation in homes which are very poorly heated or not heated at all. In fact, in these situations they can make matters worse.

We do not sell these units mail order or supply ‘quotation only’ installations. There are too many consumers with expensive equipment installed, which doesn’t address the real cause of their dampness and mould. We believe that ventilation equipment needs to be chosen to meet the evidence mentioned earlier.  Success is guaranteed only when the solution is driven by a competent survey.

Single room heat recovery systems.


In some cases, our revolutionary alternate flow single room extract with heat retention model is specified. This unit acts as a PIV and an extract system in one room. Air is extracted through the wall mounted unit for a pre-defined period, this is done very quietly. Then the unit stops and, in effect becomes a mini-PIV, reversing and drawing air into the room through the same duct.

The duct contains a ceramic heat exchange module and the heat retained in this, from the previously extracted air, is transferred to the incoming dry air.  Less efficient systems use twin ducts placed side-by-side or one-above-another. Air ‘short circuits’ can happen in these units – the alternate flow system rules this out.


What has ‘commissioning’ to do with indoor air quality?


The building regulations require that any equipment which is capable of being adjusted to variable performance must be ‘commissioned’ correctly. This is a process which we’ve included in every stage of our indoor air quality service. Commissioning means surveying the home correctly; choosing the right equipment; installing the equipment properly, adjusting and checking it’s performing as designed and finally, ensuring the end user has the documentation, instruction in use and knows where to obtain maintenance information and advice.


If you suspect that the air quality in your home is poor, or if you have excessive visible mould growth or condensation, we can help you. Our solutions are evidence driven through a proper survey and, we always get results. Call us on your local number Leeds 265 2752 York 566577 or Sheffield 224 5121 or email us via our contact page.

Further Reading:

A technical blog post explaining the difference between Relative Humidity and Vapour pressure.

For the technically minded, we’ve written a detailed article on Relative Humidity (RH) and Vapour Pressure (Vp). These are terms you’ll read in many of our indoor air quality survey reports…..

Continue reading >

If you are a Landlord with a tenant complaining about damp and mould.... you are not alone.

Whilst we offer every technical and state of the art answer for mould and poor air quality – A good pair of eyes and experience, are by far the best tools in any surveyors ‘toolbox’. Here’s an good example of modern apartments with ‘designed-in’ mould problems…….

Continue reading >

Here's a real case study from York, North Yorkshire. Our surveyor identified indoor air quality problems and now - the mould is gone for good.

Our client in York is a landlord and her tenants complained about damp and mould. After a detailed survey, which included testing of the ventilation system and measurement of the humidity – we hatched a plan. The solution was accepted, on condition that we proved the results with data logging – Our very own bpec qualified domestic ventilation engineer Paul Glover CSRT, accepted the challenge…..

Continue reading >

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