Written by Darren Pinnick managing director of Beat Solutions.
Sometimes you don't know what you've got until it's gone, this is certainly the lesson I found after recently moving into a rented property following the sale of our family home which we built in 2017. The move enables us to embark on a new venture building our next family home in Warsash, which we plan to build to Passive House standards.
Our last home was of timber frame construction, energy-efficient, airtight and included Mechanical Ventilation with Heat Recovery (MVHR). We enjoyed an even temperature throughout the building never suffered from condensation mould or unpleasant smells within the home. It wasn't until we moved in to the rented property that we realised how much we missed the superior quality of indoor air temperature and humidity delivered by the MVHR compared to that of the rented property which only as system 1 ceiling mounted extract fans to the bathroom and ensuite.
So let me set the scene we moved in to the rental property understanding the bathrooms are only ventilated with intermittent extractor fans, however what we didn't realise at that time the problem that laid ahead of us. The ensuite to the master bedroom has no windows only the Sun tunnel in the ceiling making it difficult to control the humidity buildup within the room. It took us a couple of days to realise the problem as when we first moved in the combination boiler wasn't working and we therefore didn't have any heating or hot water.
Once the landlord arrange for a heating engineer to get the boiler going we enjoyed our first shower and it was at that point I realised the ensuite completely filled up with steam and the the extractor fan fitted on the ceiling didn't seem to be removing. Unable to open a window to try and help ventilate the room all we could do was leave the ensuite light on so that the extractor fan wouldn't turn off as the overrun time was quite short.
Diagnosing the problem
Being an expert in ventilation testing, I was able to use our own ventilation testing equipment to measure the flow rate of the extractor fan. Testing the ensuite revealed the extractor fan was working at a flow rate of only 1.7 Litres/Second, this was significantly less than the 15 Litres/Second required by building regulations. It's important to note that the property is only about 10 years old and the requirements for ventilation under Part F of the Building Regulations haven't changed during that period, so I believe this has been an inherent problem from its original construction.
The effects of poor ventilation
It can be seen from the video above the rate of extraction was significantly under the requirement. Very quickly we realised the condensation forming at high-level on the walls and ceiling, where a result of poor ventilation. In addition I don't believe the insulation installed within the walls and that eaves level has been conducted very well as elsewhere within the property mould is forming on the coving. This suggests to me that this area of cold bridging when the warm moist air within the bathroom meets with the wall and ceiling surface is condensating. Within a few days black mould spores started to appear and progressively got worse and the photos below were taken after only being in the property for about 10 days.
It became evident that the landlord had the property redecorated between tenancies as the paint was now flaking off in areas. Armed with the actual flow rate of the extractor fans we informed the letting agent, who kindly discussed with the landlord who intern arranged for the extract fans to be replaced.
What happened next?
We came home one evening to find the extract fans had been changed. This was a pleasant surprise as the new fans were quieter and seemed to be doing a better job. A couple of days later I tested the new fans to see how they were performing, whilst it was an improvement upon the original fan the rate of extraction was only 8.5 Litres/Second still less in the requirements (15 l/s) set by building regulations.
The new fans whilst not perfect are doing a much better job of removing the moist air from the room and slowed down the rate of mould growth compared to the original fan as they now had a longer overrun time which is helping.
At the time of writing this article in December 2021 the temperature has significantly dropped from that of the September temperatures when we first moved in. The buildup of moisture air within the property as a result of poor ventilation and sleeping at night the bedroom windows steam up most days. You can see from the pictures below the amount of condensation building up on the windows every day and the mould growth building up in the corners.
This is all a result of poor ventilation, uncontrolled air movement and poor cold bridgings in the buildings construction around the ceiling/eaves and windows.
I believe this is typical of a system 1 ventilation strategy using intermittent extract fans and trickle vents for background ventilation in window frames. Whilst the ensuite didn't benefit from a openable window as an additional means of purge ventilation, I believe that to deliver quality ventilation and better indoor air quality within the property using system one isn't the answer.
Why I hear you ask? Well quite simply I don't believe you can provide sufficient background ventilation and the required rates of extraction using cheaper intermitting extract fans. Not only are they often noisy and turned off at the isolator by occupants, they require multiple penetrations in the building fabric to vent outside they are often neglected by installers with limited knowledge of ventilation and airflow which result in poor installation and subsequently underperformance. The results of which can be seen above and will now require the redecoration of the bathrooms and the subsequent upgrading of extract fans to comply with building regulations.
I don't recommend intermittent extract fans as a best practice for newbuild developments. I would certainly encourage system three continuous mechanical extract ventilation which can either be centralised or decentralised. These fans are often of better quality and deliver a more consistent rate of air changes due to their continuous use which will help prevent condensation and mould growth. If installed using a centralised unit the property will benefit from only one penetration in the building fabric meaning less heat loss unless grills installed externally improving the properties aesthetics.
For those seriously wanting to offer homeowners the best solution for indoor air quality we recommend considering system 4 (MVHR) which not only extracts from the property but also brings in fresh air mechanically to habitable rooms via an integrated heat exchanger which reduces the energy demand for the property and lowers its CO2 emissions. Whilst we appreciate the additional cost for some developers is off putting, but we strongly believe this is a real a game changer when it comes to the quality of indoor air. Benefits include filtration of incoming air, no trickle vents to windows and a maintained and controllable movement of air within the property which is second to none.
How we can help!
Starting in 2022 BEAT Solutions are providing a full design, supply and install service for MVHR systems. We believe every new build home should offer excellent indoor air quality which is why we are offering systems fully installed from £4,000. If you're interested in learning more about the benefits of MVHR and how they can help you lower Co2 emission, increase resell prices and generally offer a superior build, then please contact our sales team on 01489 565920.
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