"Overheating" refers to the condition of becoming excessively hot, a situation increasingly prevalent in homes due to various interconnected factors. This problem extends beyond mere discomfort, creating hot and humid living conditions; it also poses tangible health risks to occupants.
Overheating: Approved Document O covers the mitigation of overheating risk in new dwellings in England, providing guidance to help satisfy Building Regulations.
The aim of the document is to protect the health and welfare of occupants of the building by reducing the occurrence of high indoor temperatures, through designing and constructing the building to achieve both of the following: limiting unwanted solar gains in summer, through fixed shading devices and considered glazing design and to provide an adequate means to remove excess heat from the indoor environment.
Domestic dwellings subject to Part O will have to demonstrate compliance via one of two proposed methods outlined in Approved Document O. These methods are summarised below:
The Simplified Method: this assessment considers the size and orientation of glazing and compares the glazing area to the floor area. Window opening areas are also considered, to deliver suitable purge ventilation.
Dynamic Thermal Analysis (CIBSE TM59): this can be used to ensure dwellings comply with the document by modelling the building to predict the risk of overheating and offers a range of strategies for reducing this risk.
New homes must meet quality and insulation levels, making effective ventilation and cooling essential for comfort and regulatory compliance. We offer expert advice on these regulations and have created a CPD on overheating, exploring its causes and the benefits of ventilation to combat it.
This course will cover the following:
Combining ventilation with active cooling can offer a low carbon solution to overheating issues in residential properties and can be designed in conjunction with dynamic thermal modelling.
In most instances, a mechanical ventilation system such as MEV (Central Extract System) or more likely MVHR (Heat Recovery) forms the base of the strategy for overheating. This can then be adapted accordingly to ensure compliance with best practice guidance (CIBSE TM59).
Zehnder’s seven steps to better ventilation and cooling hierarchy consists of seven stages/options, some of which are complete standalone solutions, and others which are combined to deliver the required level of cooling capacity, including ventilation and humidity control and more.
LPID100 Low Profile Induct Fan
Acoustically treated inline extractor fans located in habitable rooms provide additional ventilation up to 4 ACH in lieu of openable windows.
Quiet in operation and ideal for running at night! Can be used in conjunction with MEV and MVHR mechanical systems.
Zehnder ComfoAir Q
Increased extract and supply rates (typically to around 2.5ACH) to provide purge requirements without the need for additional solutions.
Radial ducting ensures a balanced system and reduces noise and leakage to maintain lower running speeds
True summer by-pass and passive cooling
Modulating bypass within MVHR system constantly aims to improve the internal comfort temperature/humidity by allowing full/partial/no heat recovery depending on conditions.
Constant volume motors ensure ventilation rates are met and help overcome increased pressure drops.
Passive cooling can be activated based on external conditions that can help maximise comfort in warmer months by automatically boosting supply air rates
Zehnder ComfoTube Therm
Innovative Zehnder ComfoTube Therm ducting solutions ensure continuously insulated air distribution, so the living space is cooled and heated in an energy efficient manner.
Durable, whilst maintaining its flexible properties.
Working in conjunction with the MVHR system, sealed ground loops and a water to air heat exchanger provide pre-heating in the winter and pre-cooling in the summer on the supply/intake air.
Zehnder ComfoClime & Enthalpy
Working in conjunction with the MVHR system, this provides 1.5KW active air temperation and dehumidification via refrigerant cycle. Enthalpy MVHR cell passively reduces humidity of incoming fresh air under favourable internal/external conditions.
Works in conjunction with a centralised chiller system or reversible heat pump to provide 1.88-5.64KW of cooling capacity via the supply air of a constant volume MVHR system with Enthalpy cell.