Domestic Ventilation

The first recourse of many homeowners is to simply open more doors and windows. Whilst this seems to be a good idea, proper air flows can rarely be established using this method, and of course, the matters of security, heat loss and the ingress of unwanted pests like insects (or next doors cat) are perennial problems. The ‘Trickle vents’ built into many double glazed windows are also just too small to be the real answer, and again, are unlikely to produce the air flows needed.

Why Improving IAQ (Internal Air Quality) is Important

One of the reasons this issue is becoming more prevalent is that modern houses are being built to be more and more airtight, all in the bid to reduce heat loss and make them more energy-efficient. Figures show that on average, houses built since 2000 are more than twice as airtight when compared to those built before. One reason for this is the increased use of double and triple glazing, another that chimneys are rarely fitted, this reducing ventilation through the so called ‘chimney stack effect’ of fireplaces. Levels of indoor humidity have also been seen to rise, as in older property, this was to a degree regulated by hygroscopic materials, such as lime render.

Alarmingly Poor

All of this is backed up by a recent study which showed that the average IAQ in modern homes which are ventilated solely by trickle vents is alarmingly poor. Covid 19 has only exacerbated the problem, more of us having to spend a lot of time indoors. As long-term exposure to polluted and oxygen-depleted air is known to be associated with health issues, many are becoming increasingly worried about the long term implications.

The first step is to decide what rooms need better ventilation. The obvious ones are the so called ‘Wet Rooms’, bathrooms and shower rooms. The moisture levels in these can be very high, and where possible, it is best not to let this be spread around the rest of your home. Extractor fans are the obvious answer for these localised issues and can be found in many homes. These are typically fitted with time delays and sensors to ensure they only go on when they have to, many being rather noisy (lots of families report that their children are woken up in the night by these fans).

Kitchens, too, can need extra ventilation, the problem of cooking smells being added to the equation.

There is more to this than just fitting extractor fans throughout the home. The matter of airflow needs to be carefully assessed, cross flow and positive pressure ventilation needing to be understood and taken into account in the overall ventilation plan.

Cross Flow Ventilation

Putting it simply, if you want air to be able to properly circulate through a building you have to ensure that there are access and exit points for the air, and that these are correctly placed. Having just one route into and out of a room is not going to be conducive to good airflow, whilst locating these vents centrally in walls can lead to areas in the corners where there is little air movement.

Positive Pressure Ventilation Systems

Once the rooms producing moisture (and any bad odours) have been specified, an ‘airflow map’ of the building can be constructed. The idea here is to create ‘high pressure’ zones (by the use of fans or ducts) in the ‘dry’ areas of the home, whilst ensuring that there are sufficient exit vents in those rooms designated as ‘wet’. As with the weather, air flows from areas of high pressure to low pressure zones, in this instance towards any bathrooms and kitchens. This positive flow stops the wet air from entering the rest of the house, it instead being forced through the vents to the outside world. Such systems improve the air quality of a dwelling by dragging fresh air in and expelling any damp and smelly air outside before it can affect the rest of the building. This naturally reduces the condensation levels in the home, which can only benefit the property and those living within it.

Air Filtration Systems

To ensure that the air being brought into the home is itself clean, filtration systems of various capabilities are employed. These filters stop potentially harmful PM2.5 particulates, including pollen and diesel, from being introduced, this being especially useful if any occupants suffer from breathing problems. These filters do need to be changed, this being one of the items included in any air conditioning/ventilation service plans.

When reducing energy costs is also a  requirement, a ventilation strategy that will provide controlled ventilation whilst also recovering the heat energy from the expelled air is needed.  Such systems are known as Mechanical Ventilation with Heat Recovery, otherwise called Heat Recovery Ventilation (MVHR). Correctly planned and installed this form of ventilation cuts out almost all of the heat losses that are normally associated with other ventilation systems. As this loss can amount to as much as 30% of the energy used to heat a dwelling, its use at a time when everyone is trying to reduce their carbon footprint must be applauded. No other ventilation method offers such a predictable and consistent method of providing the required amount of fresh air, as well as extracting stale and polluted air.

Which MVHR System Should You Choose?

Selecting the best MVHR system is not easy and is really best left to the experts, such as Sparta Mech. After we have discussed your needs and surveyed your property we will show you the options, ones that fit within your timescales and budget. As with anything, there are cheaper and more expensive types, each one having its own limitations and advantages. But don’t worry, we will go through all of this with you, ensuring that the system we install for you is the very best possible fit for your needs.

What Does an MVHR Installation Look Like?

The heart of an MVHR system is a large unit which includes the heat exchanger. This is normally placed in the loft or some other ‘out of the way’ location. However, as frequent access is required to service the unit, such as changing the air filters, it should be easily accessible. Fans move the air to and from the system through a series of ducts and grills (this being one reason that retrofitting such systems are harder and thus more expensive than when working on a new build home). The positive airflow needed to drive air to the rooms containing the ‘stale/wet’ air is thus created, and air quality in all the rooms improved.

The most critical part of the process is not only all about the selection of the best MVHR unit, but in the planning and type of ducting that is to be used. There are three types of ducting that can be employed, PVC, Galvanised spiral ducting and Radial semi-rigid ducting. Whilst PVC is the cheapest option, it does not offer the same airflow qualities and is not as hygienic as its metal counterparts. Again this is a matter to be discussed with you when planning your homes’ ventilation system.

Please contact us to discuss your requirements, we know we can help.