Retrofit For The Future: Reducing Energy Use In A Belfast Property

Retrofit is the introduction of new materials, products and technologies into an existing building to reduce the energy needed to occupy that building.

Following on from last issue’s general introduction to the theme, this month we are looking at retrofit in action in North Belfast, at a mid terrace solid wall house built in 1896.

Major work at the property in 2001 included installation of double glazing, a non-condensing gas boiler and partial dry-lining. Retrofit for the Future included:

•  Phenolic internal wall insulation bonded to 18mm OSB, phenolic insulation to the solid ground floor and a combination of insulation types to attic ceiling;
•  Passivhaus certified windows;
•  Solar PV panels;
•  MVHR;
•  Highly insulated pre-fabricated roof

From the outset, the design team worked to a solution that prioritised the resident. They sought to choose appropriate technologies with straightforward controls that would provide a comfortable and easily controlled environment.

The main contractor took on the role of retrofit coordinator, overseeing the installation of all energy measures and closely managing sub-contractors.

During the systematic destruction before the retrofit, the team encountered numerous structural and safety concerns that needed to be addressed. This added unforeseen time and cost.

When it was discovered that the original roof timbers were decayed, a prefabricated roof with a high level of insulation was commissioned. The old roof was removed and the new roof lifted on and made weather-tight within 24 hours.

The team considered daylighting and airtightness as part of the overall strategy and commissioned innovative Passivhaus certified, inwardly opening windows that had not been produced before.

Before the retrofit, airtightness was over 12 m3/m2/hr @50Pa. Through the retrofit this was reduced to 0.25 m3/m2/hr @50Pa. This was achieved through attention to detail, driven by the retrofit coordination team and involving all sub-contractors. The whole on-site team were present at airtightness tests.

Intermediate floor joists were cut short and slotted into a steel universal beam positioned within the thermal envelope, the rotting roof was replaced with an off-site, pre-fabricated construction, and 1.6km of sealant tape was used. A user-friendly, hybrid ventilation system and controls were designed, which combined active ventilation from the MVHR with passive ventilation via automatically opening roof windows.

A straightforward services strategy included an efficient gas boiler with flue gas heat recovery, PV and MVHR. The boiler has an interlock that prevents operation unless the MVHR is running and windows are closed.

The main contractor took full responsibility to ensure any on-site changes kept to the overall strategy. They even returned to make sure a service penetration, created subsequently when broadband was installed, was sealed and airtight.

The project team spent time living in the property to fully understand its operating characteristics and optimise the systems. The handover process included guided tours and instructions with followup visits to check the residents were happy with the controls and how the house was working.

For more info about retrofit and the Technology Strategy Board, visit www.innovateuk.org