new one
By Ellen Huelin, Head of Sustainability at Whitecode Design Associates
When undertaking the MEPH designs for high-rise residential or mixed-used developments in London's bustling metropolis, the compatibility of acoustics and overheating requirements proves to create something of a dilemma for designers. With both of equal value to occupant health and wellbeing, which design considerations can be made to reduce the likelihood of overheating without compromising acoustic performance?
At present, in part L of the building regulations overheating isn't an area that is covered comprehensively. Although it is alluded to - albeit rudimentarily - in SAP requirements, its absence from the building regulations doesn't suggest that overheating is an important area when in fact it is.
Here at Whitecode, we use the CIBSE (Chartered Institution of Building Services Engineers) TM 59 guide as basis for overheating assessments. As a rule of thumb to prevent overheating, we suggest to our clients that the total glazed area per dwelling should not exceed 25% of the total floor area. On developments where windows don't have to be closed, we express that around 60% of glazing should be openable. Whilst this is all well and good and perfectly workable on high-rise developments open windows can be hazardous, particularly in terms of the windier conditions which worsen as a building reaches higher into the sky. This interference from the outside world is something which we as designers cannot change, hence the reason why acousticians are brought in to stipulate the passage of sound which needs to be controlled.
Here we have arrived at a crossway. Acoustics and overheating contradict one another. Typically, or traditionally, we open up the windows to prevent overheating. But if you are in a busy part of central London, then the acoustic requirement will be that all the windows have to be shut. Each of them is essential to assuring occupant health and wellbeing, where both the perfect temperature and sound level must be achieved.
Where does this leave overheating?
The long-awaited Acoustics, Ventilation & Overheating: Residential Design guide which was published in January 2020 recognises that a relationship between the two is needed. Clearly, the harmonisation of acoustics and overheating is on the industry's radar, and this is highly encouraging.
Typically, it is best practice to work with an acoustician at the pre-planning stage to see whether the design is going to work. For any plan which is sent to the GLA (Greater London Authority) it is recommended to complete dynamic thermal modelling as part of the CIBSE TM 59 guide. This as-built simulation enables designers to picture the building in its operational state. Consequently, this method allows overheating to be evaluated, where designers can view and access the finer details to change how far windows can open and whether they can be open overnight. This early engagement is really essential to assuring the harmony of the many aspects which go into a building.
However, if noise levels are too high or the designs have already attained planning permission, then other solutions have to be sought to ensure occupants have good air ventilation without an excess of noise.
What are the options?
Louvres, or acoustic louvres, are a great start and can be installed as an alternative to a glass window. Although louvres come at an extra cost and certainly change the visual aesthetic of a building, depending on size they can ensure sufficient airflow and acoustic control.
If the designs have already been granted planning permission, passive measures such as blinds and external shading can be considered to lessen the impact of direct sunlight. Cooling is another option however this comes at a higher cost. Cooling is also seen by the GLA as something of a last resort, as this body wants to maximise the levels of natural air as much as possible.
MVHR (Mechanical Ventilation with Heat Recovery) is a great possibility. It isn't a type of air conditioning but rather, a whole house system which uses an 'intake-and-extract' method to enable the circulation of clean air. However, whilst this solution is suitable for increasing air quality, in most cases it simply isn't enough to reduce overheating across an entire development. Extra cooling can be integrated as this additional solution decreases the temperature of the air coming in. But this is again another cost; it can also be more complicated to install and has a higher footprint as it runs off electricity. Air source heat pumps in residential dwellings are another possibility which can heat and cool spaces, yet again they are typically large and come at a cost.
When it comes to changing a design that has already passed planning permission, there are few options. It is why it is paramount to engage all specialist parties - MEPH, architects, acousticians, etc. - from the earliest point of the building's design. Working altogether from the very beginning will harmonise a building's temperature and sound levels, and will ultimately be the defining aspect of whether a space is comfortable for its occupants.
ENDS
For further information please contact David Ing, Fabrick:
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By Ellen Huelin, Head of Sustainability at Whitecode Design Associates When undertaking the MEPH designs for high-rise residential or mixed-used developments in London's bustling metropolis, the compatibility of acoustics and overheating requirements proves to create something of a dilemma for designers. With both of equal value to occupant health and wellbeing, which design considerations can be made to reduce the likelihood of overheating without compromising acoustic performance? At present, in part L of the building regulations overheating isn't an area that is covered comprehensively. Although it is alluded to - albeit rudimentarily - in SAP requirements, its absence from the building regulations doesn't suggest that overheating is an important area when in fact it is. Here at Whitecode, we use the CIBSE (Chartered Institution of Building Services Engineers) TM 59 guide as basis for overheating assessments. As a rule of thumb to prevent overheating, we suggest to our clients that the total glazed area per dwelling should not exceed 25% of the total floor area. On developments where windows don't have to be closed, we express that around 60% of glazing should be openable. Whilst this is all well and good and perfectly workable on high-rise developments open windows can be hazardous, particularly in terms of the windier conditions which worsen as a building reaches higher into the sky. This interference from the outside world is something which we as designers cannot change, hence the reason why acousticians are brought in to stipulate the passage of sound which needs to be controlled. Here we have arrived at a crossway. Acoustics and overheating contradict one another. Typically, or traditionally, we open up the windows to prevent overheating. But if you are in a busy part of central London, then the acoustic requirement will be that all the windows have to be shut. Each of them is essential to assuring occupant health and wellbeing, where both the perfect temperature and sound level must be achieved. Where does this leave overheating? The long-awaited Acoustics, Ventilation & Overheating: Residential Design guide which was published in January 2020 recognises that a relationship between the two is needed. Clearly, the harmonisation of acoustics and overheating is on the industry's radar, and this is highly encouraging. Typically, it is best practice to work with an acoustician at the pre-planning stage to see whether the design is going to work. For any plan which is sent to the GLA (Greater London Authority) it is recommended to complete dynamic thermal modelling as part of the CIBSE TM 59 guide. This as-built simulation enables designers to picture the building in its operational state. Consequently, this method allows overheating to be evaluated, where designers can view and access the finer details to change how far windows can open and whether they can be open overnight. This early engagement is really essential to assuring the harmony of the many aspects which go into a building. However, if noise levels are too high or the designs have already attained planning permission, then other solutions have to be sought to ensure occupants have good air ventilation without an excess of noise. What are the options? Louvres, or acoustic louvres, are a great start and can be installed as an alternative to a glass window. Although louvres come at an extra cost and certainly change the visual aesthetic of a building, depending on size they can ensure sufficient airflow and acoustic control. If the designs have already been granted planning permission, passive measures such as blinds and external shading can be considered to lessen the impact of direct sunlight. Cooling is another option however this comes at a higher cost. Cooling is also seen by the GLA as something of a last resort, as this body wants to maximise the levels of natural air as much as possible. MVHR (Mechanical Ventilation with Heat Recovery) is a great possibility. It isn't a type of air conditioning but rather, a whole house system which uses an 'intake-and-extract' method to enable the circulation of clean air. However, whilst this solution is suitable for increasing air quality, in most cases it simply isn't enough to reduce overheating across an entire development. Extra cooling can be integrated as this additional solution decreases the temperature of the air coming in. But this is again another cost; it can also be more complicated to install and has a higher footprint as it runs off electricity. Air source heat pumps in residential dwellings are another possibility which can heat and cool spaces, yet again they are typically large and come at a cost. When it comes to changing a design that has already passed planning permission, there are few options. It is why it is paramount to engage all specialist parties - MEPH, architects, acousticians, etc. - from the earliest point of the building's design. Working altogether from the very beginning will harmonise a building's temperature and sound levels, and will ultimately be the defining aspect of whether a space is comfortable for its occupants.
ENDS For further information please contact David Ing, Fabrick: |
