The Importance Of Ventilation In Your Home
Why ventilation is important in your home
The average British person spends 90% of their time indoors, either in the workplace or at home, as technology has replaced the need to run errands or socialize outside. As a nation we are also investing much more on home improvements—whether for positive reasons—perhaps we are part of the post-pandemic trend of increased working from home, or more from economic necessity, because high mortgage rates and other costs of moving make it more sensible to make changes to our current property instead, or because the costs of heating our homes has spurred us to make improvements for the long term. Many are insulating lofts and walls and installing new windows, as well as building extensions.
Whilst we often think in terms of specific areas that we want to improve, we should be applying “whole house” strategies to ensure we are upgrading in a way that doesn’t lead to unintended consequences—either undermining the performance of “improvements”, or even worse, creating significant hazards.
40% of the UKs housing stock was built before 1919 with natural materials and ventilation systems. We say that these buildings are built to “breathe”. In the drive for energy efficiency in retrofitting our homes with insulation and making them more airtight with new windows and doors, we reduce this natural breathing capacity which provides a constant flow of ventilation (most people think of this as “leakiness!”). This is “uncontrolled” ventilation since we can’t fine tune it and it is often more than we need, thus not great for our heating bills, but a basic amount of ventilation is necessary for our health and the health of our homes.
An insulation installer who is responsible for one element won’t necessarily remind you to consider the impact of the improvement on ventilation and recommend to get the ventilation tested and improved. Even a general builder responsible for making a number of upgrades around the house may not fully understand at what point it becomes necessary to augment ventilation. To make matters more confusing, building regulations have been quite lax in this regard and were only strengthened last summer (2022) when the new Part F came out. Even though these new requirements are quite clear, they are relevant to the whole house, and are not the responsibility of a supplier of any one element in the house. So anyone without an architect or overall project manager for their upgrade may miss this key element.
As a result, condensation and mould are on the increase and common in many homes across the UK.
Trapped humidity can cause respiratory illness such as asthma and other conditions like eczema. We also need good ventilation to ensure that VOCs (volatile organic compounds) within our daily life from hairsprays, perfumes, aerosols, cleaning products, furniture glues and paints are dispersed from the internal environment. VOCs have been linked to nervous system damage and also cancer.
Homes need fresh air intake and to flush out humid, dirty air. Many people use what we call “active” ventilation habits, like opening a window when cooking or showering, but this varies greatly amongst the population and of course, people will tend to use natural ventilation less freely in colder months, though our needs don’t decrease. As we improve our homes, by insulating and making them more airtight we need to implement measures to ensure we don’t reduce this airflow. In some cases mechanical ventilation will be the best solution, especially if it can be coupled with heat recovery to reduce its energy consumption.
‘Build tight, ventilate right’
This phrase has been coined by the industry and is a “first principle” for retrofit. Ventilation has been a requirement for new-build (including extensions and major renovations) for decades but never more than a recommendation when installing energy efficiency into existing homes until now.
There are two options: decentralized ventilation and centralized systems. Decentralized means that each room is evaluated on its merits, in terms of how much damp is generated in the room, whether or not it can be cross-ventilated and how air-tight it is. In this scenario, measures such as trickle vents to windows in all rooms, extractor fans in wet rooms (kitchen, bathrooms, utilities… any room with running water but also rooms in which laundry is regularly air-dried) and 10mm gaps under all internal doors capable of providing cross-ventilation from room to room each play a key part in ensuring that overall ventilation is achieved.
These measures will probably provide sufficient air flow in homes that are not fully insulated, but as we insulate walls in addition to draughtproofing and double-glazing, then a whole-house mechanical ventilation system is likely to be required. These systems can be easy or difficult to fit in existing homes, depending on their complexity. The main drawback is that these systems use a good deal of energy, so the goal of insulating to achieve energy-saving is not as straightforward as it might seem. In some cases and for older homes in particular, in order to achieve the maximum energy reduction, it can be a better option to insulate a little less in order to find a sweet spot where decentralized ventilation will provide the required air flow.
In any case, don’t ignore your ventilation needs. These are of vital importance and unfortunately, unless you have a Retrofit Coordinator, Architect or other person in charge of designing and delivering your complete upgrade package, according to building regulations, this aspect can be lost amongst the insulation boards.
