Home Ventilation: Creating a Well Ventilated and Healthy House

Home ventilation is an extremely important part of creating a healthy living environment. And, in the drive to keep energy bills to a minimum while achieving high standards for heat efficiency, self builders and renovators are doing all they can to pack in plenty of insulation and establish an airtight thermal envelope.

However, when laying out the plans for your future home, don’t overlook the importance of indoor air quality and the impact it can have on health and wellbeing. If you build a highly airtight house but fail to think through your home ventilation strategy, you risk creating an internal atmosphere akin to that of a plastic bag or Tupperware container.

One essential benchmark for a healthy and well ventilated home is a comfortable indoor air temperature that can be achieved in an energy efficient way, in terms of both heating and cooling. But this shouldn’t be done at the expense of air quality. “A healthy home should also manage humidity and airborne pollutants,” says Darren Johnson, managing director at Air Craft.

It may surprise you to learn that, in some scenarios, indoor air quality can be up to five times worse than outside a building. “This is due to breathing (CO2), micro particulates, cooking smells and fumes, pet dander, dust mites and volatile organic compounds (VOCs) found in paint and furniture,” says Darren. So, what are the dangers of not planning your home’s ventilation properly, and what steps can you take to ensure you get a home ventilation setup right?

Why Do I Need Good Home Ventilation? 

Bad home ventilation can feel stuffy and stifling, creating an environment that will likely lead to condensation buildup on the walls and ceiling. This, in turn, will spark further issues affecting occupants’ wellbeing, such as the growth of harmful bacteria – not to mention potential damage to the structural fabric. “New build homes are highly efficient, better insulated and more tightly sealed than ever. But there are already instances of new houses requiring better mechanical ventilation,” says Madeleine Brighton from Unico Systems.

If home ventilation isn’t addressed, there’s an increased likelihood that trapped contaminants will flourish, possibly leading to a negative impact on occupant health. “This is especially the case for those who have allergies, asthma, other respiratory difficulties or immune system deficiencies. The effects of humidity and condensation can also lead to mould growth on the walls and window frames,” says Madeleine. Good design from the earliest planning stages is therefore crucial – so speak to your architect and ventilation specialists early to ensure it’s designed in from the start.

Planning your new healthy, sustainable self build home? Take a look at this collection of 20 Sustainable Eco Homes to Inspire Your Project

In this home ventilation setup by Total Home Environment, insulated ducts have been installed as air pathways within a mechanical ventilation and heat recovery system. Rigid metal ducting typically offers the best performance, as flexible tubing is easier to damage (plus its curves can adversely affect airflow)

When considering your strategy for a home ventilation, another key pitfall to avoid is building a house that suffers from overheating. This usually occurs due to excessive solar gain as a result of installing broad expanses of glazing. “Most people don’t appreciate that ventilation alone will not solve this problem and they may need comfort cooling, too, via the likes of a heat pump system,” says Darren.

Updates to Building Regulations back in June 2022 incorporated a new Approved Document O, which looks at how to mitigate the effects overheating. Part F of the regs covers home ventilation, while Part L looks after energy efficiency.

Learn More: Designing Out Overheating in Modern Eco Homes

How to Get Home Ventilation Right

Most properties will be built with good home ventilation features. This includes trickle vents, airbricks and natural solutions (ie opening windows and relying on breathable building fabric) to ensure the removal of stale air and the introduction of a fresh supply.

Most houses are also kitted out with straightforward, cost-effective extractors in the bathroom and kitchen. The trouble with such home ventilation solutions is that the rate of air change is uncontrollable, and over-ventilation can lead to heat losses that negate the benefits of a high-performance structural fabric. So, what are the controllable options of home ventilation? Broadly speaking, they fall into one of three categories:

Mechanical ventilation and heat recovery (MVHR) removes stale air from the home and draws in a fresh supply. In the process, it extracts and recycles heat from the outgoing stream before transferring it to the incoming channel. “MVHR is the only type of ventilation to ensure waste heat isn’t just chucked outside. Properly designed and installed, it can reduce heating bills by about a third,” says Clarissa Youden, associate director at Total Home Environment.

A fan-powered air-handling unit in the attic or plant room is the beating heart of the setup. This is connected to a network of ducts and extract/supply points throughout the house. Old air is drawn out of each room (especially bathrooms and kitchens) and passes through a heat exchanger before being released outdoors. The warmth is then introduced to the fresh flow of air which passes into each zone via the network of ducts.

Mechanical extract ventilation (MEV) features a network of ducts connected to numerous terminals in the house. A central unit, usually in the loft, draws stale air upwards and expels it through an opening on the roof. The setup runs 24/7 and detects spikes in humidity, at which point the ventilation goes onto boost mode. However, this type of home ventilation system can’t provide the extra boost of warmth from a heat recovery setup.

Positive input ventilation (PIV) comprises a small fan-powered unit, typically in the attic, which brings in fresh air from outside. The inbound stream is pushed through the property via a network of ducts. Air that’s heavy with moisture is diluted and displaced – pushing it out of the building – to keep humidity levels under control. This kind of home ventilation system is most frequently specified for retrofit projects.

The central air handling unit of this Unico system is installed in the loft. The setup comprises a series of small ducts that mix and deliver conditioned air into the living space

Further House Ventilation Tips for a Healthy Home

In addition to effective home ventilation systems, such as MVHR, improved indoor air quality can be achieved via the selection of healthy materials and finishes. “Choose eco paints, detergents and building fabrics that don’t emit VOCs,” says Clarissa. “You could also invest in a few house plants, which will absorb carbon dioxide and release oxygen during the day – it’s best not to have them in bedrooms, however, as they do the opposite at night.”

Minimising the risk of overheating is another important element within any approach towards home ventilation. For instance, incorporating external shading to large areas of glazing is one way to reduce excessive solar gain. This should be factored into the design at the outset of your project, so your architect can develop a solution that maximises the low angle of the sun during winter and limits exposure from the higher angle of the sun’s rays during summer.

“Another option is to incorporate opening windows that sit opposite each other so you can perform a purge ventilation at night, when external temperatures are cooler than inside the house,” says Clarissa. “This will help your MVHR system to bring the temperature inside the house down to a more clement level for sleeping.”

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