Zero direct emissions heat in new build affordable homes: Stornoway, Isle of Lewis
Hebridean Housing Partnership (HHP) has been operating across the Outer Hebrides since 2007. It has c.45 staff and over 2200 properties and has been installing heat pumps since 2010. HHP has vast experience with both heat pumps (which are utilised in 52% of their homes) and direct electric systems (utilised in 25% of their homes). Air Source Heat Pumps (ASHPs) were selected for this development as fuel poverty is a major concern in the Hebrides and HHP deemed them to be cost effective for tenants on this basis.
Heating system installation
The development was designed and constructed under a traditional build contract, and features 50 unique units. The ASHP model was specified and installed by the main contractor, for £9,100-£9,500 per unit. Care was taken to locate the external units to: minimise pipework lengths to internal cylinders, minimise noise impacts (i.e., away from bedrooms), and satisfy planners (i.e., not at the front of the homes). There were no issues associated with installing the ASHPs and no impacts on grid connection costs.
Handover process
Between completion and handover, HHP turned on the ASHPs to run at 12oC. At handover, HHP and the contractor were onsite to show tenants how to run their heating systems correctly. User guides were also provided, which advised tenants to use only the wireless zone thermostats to control the heating (and not the heat pump’s inbuilt programmer). Tenants were also advised to call HHP if issues with heating arose, and to not attempt to fix these themselves.
Tenant impacts
In the Hebrides, ASHPs are common as only Stornoway is served by a gas grid, and there has been a drive to educate the population on heat pump principles. Therefore, tenants now expect these in new homes, and do not need as much handholding as previously. Tenants are asked to feedback on their heating systems during annual visits, and over 95% are satisfied with their heating systems. No tenants have indicated they are unhappy with their bills. Only one complaint has been raised, by a tenant in an open-plan bungalow who did not feel that all of their living area heating zone was reaching the thermostat’s set temperature. This was resolved by advising the tenant to close doors to other rooms.
Technical performance
The maintenance schedule consists of annual services by an external contractor, and the first of these was free as it was conducted during the defects period. There have been no unplanned maintenance requirements at MacKenzie Avenue. HHP has found that it is important not to undersize heat pump capacity, as larger units will tick over and last longer than smaller ones always operating at maximum capacity. Some of the ASHPs have 4G connections which allow HHP to see the output temperatures and status remotely. This has been very useful for ensuring performance and is expected to support future troubleshooting.
Lessons learned
Tenants from older buildings appreciate that the costs of heat pumps in newbuilds are low, regardless of their previous heating technology.
Selecting the right heat pump is important: this model has an optional coating for salty air, making it suitable for the development’s coastal setting.
Technical issues have been completely avoided due to close teamwork and trust between the housing provider, ASHP manufacturer, and the installer.
Produced by Locogen Ltd and Hebridean Housing Partnership as part of the Evaluation of Heat in Affordable Housing (Phase 2) for the Scottish Government. July 2022.
Source: The Scottish Government