New rules relating to heating and cooling buildings are set to come into force in June this year.
Section O of the Building Regulations 2010 will be effective from June 15 to protect the health and welfare of a building’s occupants.
It will cover the design and construction of buildings to achieve two key objectives relating to limiting high indoor temperatures:
a. Limiting unwanted solar gains in summer
b. Providing an adequate means of removing excess heat from the indoor environment
The strategy to reduce overheating risk should be selected according to the location of the new residential building and whether it has cross-ventilation. – i.e. it has openings on opposite façades.
A multi-occupancy residential building should not be categorised as having or not having cross-ventilation. Each residential unit, shared communal room and common space should be categorised separately
The new guidelines detail a dynamic thermal modelling method for demonstrating compliance with requirement O1.
To demonstrate compliance using the dynamic thermal modelling method, all of the following guidance should be followed: CIBSE’s TM59 methodology for predicting overheating risk.
All of the following limits on CIBSE’s TM59, section 3.3, apply:
a. When a room is occupied during the day (8am to 11pm), openings should be modelled to do all of the following. i. Start to open when the internal temperature exceeds 22°C. ii. Be fully open when the internal temperature exceeds 26°C. iii. Start to close when the internal temperature falls below 26°C. iv. Be fully closed when the internal temperature falls below 22°C.
b. At night (11pm to 8am), openings should be modelled as fully open if both of the following apply. i. The opening is on the first floor or above and not easily accessible. ii. The internal temperature exceeds 23°C at 11pm.
c. When a ground floor or easily accessible room is unoccupied, both of the following apply. i. In the day, windows, patio doors and balcony doors should be modelled as open, if this can be done securely, following the guidance in paragraph 3.7 below. ii. At night, windows, patio doors and balcony doors should be modelled as closed. d. An entrance door should be included, which should be shut all the time.
Limiting solar gains in summer should be limited by any of the following means:
a. Fixed shading devices, comprising any of the following. i. Shutters. ii. External blinds. iii. Overhangs. iv. Awnings.
b. Glazing design, involving any of the following solutions. i. Size. ii. Orientation. iii. g-value. iv. Depth of the window reveal.
c. Building design – for example, the placement of balconies. d. Shading provided by adjacent permanent buildings, structures or landscaping.
Although internal blinds and curtains provide some reduction in solar gains, they should not be taken into account when considering whether requirement O1 has been met, likewise the existence of foliage, such as tree cover.
Excess heat should be removed from the residential building by any of the following means: a. Opening windows (the effectiveness of this method is improved by cross-ventilation).
b. Ventilation louvres in external walls.
c. A mechanical ventilation system.
d. A mechanical cooling system
Buildings should be constructed to meet requirement O1 ‘using passive means as far as reasonably practicable’, note the regulations. ‘It should be demonstrated to the building control body that all practicable passive means of limiting unwanted solar gains and removing excess heat have been used first before adopting mechanical cooling. Any mechanical cooling (air-conditioning) is expected to be used only where requirement O1 cannot be met using openings.’
In locations where external noise may be an issue (for example, where the local planning authority considered external noise to be an issue at the planning stage), the overheating mitigation strategy should take account of the likelihood that windows will be closed during sleeping hours (11pm to 7am).
Buildings located near to significant local pollution sources should be designed to minimise the intake of external air pollutants.
When determining the free area available for ventilation during sleeping hours, only the proportion of openings that can be opened securely should be considered to provide useful ventilation, particularly in relation to ground floor or easily accessible bedrooms.
In addition, only the proportion of openings which can be opened with a very low risk of occupants falling from height should be considered to form part of the overheating mitigation strategy.
When a new residential building is erected, information about the building and its overheating mitigation strategy must be given to the owner of the building to allow them to use the strategy effectively
A home user guide should be provided for new residences with non-technical information on staying cool in hot weather.
Demonstrating compliance with the new Part O building regulation should be a priority now for housebuilders, warned Syntegra MD Alan King.
He said: ‘Recent changes to regulations have led to buildings being much better insulated but in turn, that leads to an increased likelihood of overheating. This is set to become an even more widespread issue as the climate gets warmer.
‘Therefore these are welcome changes to improve the comfort and wellbeing of residents in new buildings.’
Mark Standen, Syntegra’s Director of Energy and Sustainability, said: ‘This clarification is a major step forward as the construction industry continues to shine a light on sustainable solutions to tackle climate change and associated concerns.
‘These are some very practical, relatively easy to include, measures which will make a tremendous difference to the lives of people living in buildings susceptible to overheating.’
According to the Department for Levelling Up, Housing and Communities, there are about 2,000 heat-related deaths in the UK every year, which is anticipated to triple by 2050 due to climate change.
Any building started after the June launch date must be up to the new standard within a year.
You must be logged in to post a comment.