Sweating it out: the overheating headache
Doug Johnson
Like it or not, our climate is warming and becoming more unpredictable. Weather is becoming more extreme, and winters are warmer than they have ever been. Combined with the rapid pace of materials development, new construction techniques, and our increasingly obsessive behaviour concerning building energy losses; there is a big issue. It is calculated that over 4.5 million buildings a year suffer from overheating, with the vast majority of those being newly constructed.
In fact, the problem has become so much of an issue that the regulation of building overheating in the 2021 Building Regulations under a new section - Part S - is also expected to come into force in Q1 2022 to ensure that sufficient due diligence is undertaken for new buildings.
Paradoxically, as we advance and focus on highly insulated buildings with managed ventilation and less natural air infiltration, we make the very buildings we hope to be fit for purpose and progressive, become uninhabitable and uncomfortable. In addition, in trying to reduce build costs and improve the speed of construction, the very materials and techniques that make this possible go against some fundamentals of building physics which have for centuries allowed buildings to remain comfortably cool throughout the year.
The real risk to developers of ignoring the threat or possibility of overheating is that once a project is completed, to resolve overheating issues costs considerable money and time to put even partially right. As an afterthought, this can not only be expensive but ugly and will invariably add to the long-term running and maintenance costs of the build.
The good news is that this risk can be mitigated by some increased understanding of what causes it and basic analysis at the conceptual design and pre-planning stages.
Top 3 Causes of Overheating
There are three main causes of overheating in buildings. We will quickly cover these as well as how to reduce their impact.
1. Low thermal mass
The density of the materials used in a structure strongly affects daytime overheating and the long-term retention of heat or cool in the structure. Lightweight structures such as SIPS and timber-framed buildings respond far quicker to high exterior temperatures. Higher density structures such as masonry and concrete respond far more slowly and peak daily internal temperatures remain lower on even the hottest days of the year.
2. Large areas of glazing
High proportions of glazing above 35% of the total wall area on east, south or west building elevations can be a significant cause of detrimental solar gains in spring, summer, and autumn. Where increased levels of glazing are desired, solar shading should be investigated and engineered to ensure fully functional and appropriate use for the building type.
3. Poor natural ventilation
The poor ventilation of spaces, particularly at night-time, in domestic dwellings is a great cause of overheating in homes. More generally, a lack of air movement or cross-ventilation in buildings can quickly become a nuisance and lead to high levels of discomfort. Single aspect buildings such as flats are a particular example, and the use of purge ventilation should be considered at the earliest stages of design to save costs later!
The way forward
One of the most effective ways to better understand the potential overheating risks of your development as designed is to use dynamic thermal and ventilation modelling from as early as possible in the building’s design process. Costs vary based on the building size and complexity, but for as little as £1,000 +VAT you can have a detailed first pass of the design and quickly identify room-by-room where any issues may lay. Once digitally modelled, as the design develops, an intelligent and focused approach can be taken providing feedback to the design team as to appropriate changes with a high level of confidence in performance once built.
How Mesh can help
At Mesh, our analysis eradicates overheating from a property by using a step-by-step high end calculated approach. We take all the necessary steps and passive design strategies to not only reduce/remove overheating from a property, but also to reduce energy bills. We can perform calculations related to Part O compliance, TM59, TM52, general overheating and planning for new builds, as well as provide solutions for domestic and non-domestic projects. Mesh believes in using the most resourceful passive design strategies to remove/reduce overheating in both new build and retrofit projects.
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