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Residential Key Design Considerations

The residential sector, particularly new build central London schemes has become very prominent in recent years.

 

Matthew Thurston, Client Services Director at hurleypalmerflatt gives you some of his engineering lessons learnt within the residential market.

 

With the level of central servicing potentially including centralised chp, heating, cooling, ‘Whole House’ ventilation and intensive AV and security requirements the design of the engineering services is a key element to the success of any scheme. Minimum Energy Standards (Code for Sustainable Homes) also has a major bearing on this as well as Part L and other statutory planning requirements. Early establishment of the brief and interface between landlord and occupier is critical both spatially (risers and plant etc) and operationally.


Some of the key design factors and ‘lessons – learnt’ that should be considered on any future schemes are highlighted below:

 

Apartment heating and hot water requirements
To meet planning, statutory and minimum energy standards (CfSH), Centralised CHP/heating systems are often adopted due to the potential for future replacement with Low or Zero Carbon (LZC) technologies, as well as offering potential economies of scale in respect to efficiency – therefore reduced carbon emissions.


Common practice is to specify Heat Interface Units (HIU’s) to provide hydraulic separation between primary and secondary pipework, and allow for the generation of heating/cooling and hot water within each apartment.


Utilizing diversity or coincidence factors for hot water demand, such as the Danish Standard DS439, help to avoid gross system over sizing, and are based upon data obtained from years of European and Scandinavian community heating studies.

 

Early spatial co-ordination
Typically spatial planning of apartment utility cupboards is required at an early stage to ensure that appropriate allowances have been made for plant items required to fulfil the client brief. Items such as the HIU heat exchangers (as outlined above), hot water cylinders, ventilation equipment, and consumer units need to be accommodated within each apartment, and often have to be integrated amongst storage shelving and washer dryers.


Area and value is at a premium, particularly in congested city developments and the layout of apartments critical to a successful marketing strategy. Early and thoughtful consideration to the location and subsequent coordination of these requirements with the Architect and client is paramount.


During detail design the use of a prefabricated approach with specialist suppliers/contractors is an efficient and cost effective method that should be considered. With the significant increase in occupier AV, comms and data requirements the location of these services within central cupboards/risers etc, needs careful consideration with regard to extraneous heat build up etc.

 

Corridor overheating
Due to the increase in the use of centralised heating and CHP in residential schemes, the problem of communal corridor overheating has been brought to the attention of many developers and design teams.


Poorly insulated heating pipework distributed within long, unventilated, internal corridors can cause a significant build up of heat, especially during summer months.


Mitigation measures can include the installation of dedicated fans or by utilising the smoke extract fans linked to a thermostat to ventilate the corridors. Other passive measures such as enhanced pipework insulation, PIR controlled corridor lighting, and vents to the top of riser shafts can assist to help reduce the risk of heat build up.

 

Ventilation strategies
As a consequence of designers having to find cost effective ways of meeting more demanding carbon emission reduction targets, ‘Whole House’ Mechanical Ventilation with Heat Recovery (MVHR) systems are being increasingly specified to help achieve Part L compliance and attain the desired Code for Sustainable Homes level.


Each individual system continuously extracts moist and polluted air from kitchens and bathrooms, whilst supplying filtered fresh air to all habitable rooms via a heat exchanger.


A correctly sized, installed and commissioned system will provide positive benefits to the occupier, however there are common issues such as excessive noise levels due to undersized MVHR units and inadequately sized external air intake/exhaust terminals, to name a few. Consideration to air quality targets stated in any EIA also needs to be considered 
in detail.

 

Metering 
Metering strategies can vary depending on a number of variables for example the physical constraints of the building or the value of the development.


Gas is provided to higher end apartments, however other dwellings are generally provided with electric cooking hob facilities. In accordance with utility providers requirements, metering of electricity and water should be accessible and located within communal areas such as risers or in dedicated meter rooms. Heat or cooling is measured in kWh by a heat meter integral to the HIU.


Data is then collected onto a metering network and logged onto a site based billing server. For social housing developments, pre pay metering systems can be incorporated into the design where tenants are provided with the facility to top up online or through an on site kiosk.