Why quality counts in domestic ventilation systems

The word ‘quality’ gets bandied about all over the place. Lets face it, no sane company is going to say their products and services are not good quality. When it comes to ventilation, it is no different: everyone seemingly makes good quality ventilation products and systems. But how do you define quality and is it actually important?

1 Yes, quality matters
2 Product: make or break
3 System design: start with the ‘building blocks’
4 Installation: do not cut corners
5 A final word
6 Related articles on Designing Buildings

[edit] Yes, quality matters

In the world of ventilation, quality really does matter. Using poor quality products will most likely result in a ventilation system that is unable to deliver the air flow required to comply with Building Regulations, and make for an uncomfortable environment in which to live. But that is not all; it could also make for a noisy system and one that leaks condensation onto walls and ceilings, leading to the formation of mould which is not only unsightly but can be hazardous to health.

[edit] Product: make or break

With whole house ventilation systems featuring Mechanical Extract Ventilation (MEV) and Mechanical Ventilation with Heat Recovery (MVHR) as the main means of meeting the revised Part F Ventilation of Building Regulations, the quality of these units can make or break a system.

A good quality unit will have a low Specific Fan Power (SFP), which reduces energy consumption and directly impacts on a property’s Dwelling Emission Rate (DER). In the case of MVHRs, the heat exchanger is a key component so be sure to check its proficiency. The heat exchangers featured within our Domus HRXE range of MVHRs enable up to 95% of waste heat to be recovered, making it highly efficient.

Important features to look for in MVHR units are a thermal bypass which automatically activates when the air temperature reaches a pre-set level, allowing in cooler, fresh filtered air without warming it through the heat exchanger; and integral humidity sensors which automatically changes the extract speed from background to boost as the level of humidity increases. The units must be listed on the SAP Product Characteristics Database (PCDB).

If MEV and MVHR units are seen as the heart of the ventilation system, they can only function efficiently if the arteries – the ducting – is of a similarly good standard. Unfortunately, this is where the majority of problems arise, as ducting quality is often forsaken for price. If you want your mechanical ventilation system to function correctly, it is imperative to invest in quality ducting that has been designed to work in harmony as part of a system and has been third party tested for end-to-end system performance.

A good quality ducting system will have exacting tolerances and push fits together for minimal air and moisture loss and maximum system efficiency. It is easy to spot poor quality ducting as the channel or pipe bows, or looks like it is concave, or the wall thickness appears uneven. And remember, never use flexible duct work in place of rigid ducting as it causes a lot more air resistance and can be crushed easily. A quality ducting system will also come with a range of useful accessories to help you meet site circumstances, such as ducting silencers, aerodynamic bends and pollutant filters such as the Domus NOX-FILT. In addition, it should be accompanied by both dedicated ducting insulation and firestopping products. Ducting insulation is particularly important to use between a MVHR appliance and the external terminals, and in the unheated areas of a property such as loft spaces.

[edit] System design: start with the ‘building blocks’

Of course, you can have the best ventilation products in the world, but if the system design is not up to scratch, then it will not lead to the results you expect. So quality matters here too.

Whilst some might think the ventilation unit should be the starting point, it is actually the ducting drawing that needs to come first; before unit specification and before the other services (gas, water pipes etc.) going in as otherwise you will need to add more duct work to get around these obstacles. Ducting drawings are not easy, but ‘quality’ manufacturers will be able to provide these for you, so be sure to take advantage of this service. Domus Ventilation provides individual system drawings free of charge, along with duct take-offs and estimations.

[edit] Installation: do not cut corners

An issue that was highlighted when reviewing the previous set of Building Regulations was the dearth of compliance. Many cited the complexity of the old Building Regulations being the issue, but deliberate changes on site to reduce costs and make for a quicker installation are also to blame.

Over the years we have witnessed just about all the mistakes that could be made on site, from installers trying to simplify duct runs to save time and money; using flexible duct work at final connections or around obstructions such as steel beams; using the wrong size air bricks and incorrect size air valves; not using ducting insulation, and a whole lot more.

With the revised Building Regulations ‘Approved Document F, Volume 1: Dwellings’ (ADF1), which came into effect in 2022, the ventilation rate calculations have been considerably simplified and reporting has been tightened up to drive compliance and, ultimately, system quality.

Opting for a quality product means you have the support of a quality manufacturer who can advise on all matters relating to specification, installation, commissioning and maintenance and, in more challenging cases, will even attend a site visit to ensure the ventilation system is not just fit for purpose but operates at its most efficient.

[edit] A final word

Quality does come at a cost and there will always be a balance between these two factors. But if quality is being sacrificed to save money, then consider this: when it comes to a whole house mechanical ventilation system, a large amount of the cost is in the labour. Good quality ventilation products and systems may come at a higher price, but they are often designed with easy – and therefore quick - installation in mind. Opting for lower cost product may well end up being a false economy.

This article appears in the Winter ATJournal number 148 as "Domestic ventilation systems: why quality counts" and was written by Paul Williams, Domus Ventilation Product Manager.

--CIAT