On the sunny side of the street - new Passivhaus homes for Belfast

Sunningdale Gardens, the Northern Ireland Housing Executive's first housing project in 25 years, is the first MMC Passivhaus certified social housing project delivered in Northern Ireland. The six semi-detached homes in North Belfast were built for £1.2 million.

Sunningdale Gardens, Belfast. Image credit: NIHE

The Northern Ireland Housing Executive (NIHE) is a large social housing landlord, but has not directly undertaken a new build construction scheme of any type in over 25 years until the Sunningdale Gardens pilot. The NIHE was the client, architect and project manager on the scheme, which is located in what is termed a 'Common Landlord Area' of North Belfast, which has experienced greater levels of social deprivation in recent years and a high housing need.

Passivhaus Consultant on the project was PHT member Mosart and it was certified by PHT member BePHit. PHT Patron AtkinsRéalis was QS and contract advisor.

Key stats

Construction: MMC single skin aerated block with EWI
Number of homes: 6 semi-detached 2-bed homes
TFA: 133.73 m² (per housing unit)
Build start date: 2023
Completed: 2024
Certified: Passivhaus, 2025

Sunningdale Gardens Belfast. Image credit NIHE

Construction

The homes were constructed with a single skin of aerated/ thermal blockwork, with EPS external wall insulation with a rendered finish, which was specified as a rapid build technique and onsite MMC (Modern Method of Construction). Internally there is a service void, insulated with PIR.

This is not just the Housing Executive delivering new homes, it is the Housing Executive leading and innovating for Northern Ireland. The Modern Methods of Construction approach and the Passivhaus standard that NIHE has achieved will together bring learning for the whole social housing sector here.

Gordon Lyons, Minister for Communities, Northern Ireland

As the strategic housing authority for Northern Ireland, it is our role to influence the future of social housing and with Sunningdale we are demonstrating what estates and housing developments can look like in the years to come.

At the outset of this pilot project our aim was not just to build new homes for our tenants for the first time in a generation but to build future-proofed homes with energy efficient measures that will stand the test of time. The ultra-low energy building methods used to construct these houses means that our tenants will now benefit from improved energy efficiency and a reduction in carbon emissions, lower heating bills, savings from reduced fuel costs and more comfortable homes.

Nicole Lappin, Chair, Northern Ireland Housing Executive

U-values

Sunningdale Gardens under construction. Image credit: GEDA Construction

Roof: 0.055 W/m²K

Cold roof build up consisting of 800mm mineral fibre loft insulation.

Wall: 0.111 W/m²K

External walls constructed of a single skin of aerated/ thermal blockwork, with 225mm EPS external wall insulation with a rendered finish. Internally an insulated service void has 25mm PIR.

Floor: 0.099 W/m²K

Ground floor build-up of sand/ cement screed on suspended precast concrete slab on 300mm EPS insulation

We are so excited to move into our new home and join the community in Sunningdale. This house will make a huge difference for my family. I am looking forward to learning how to make the most of all the energy efficient measures within the house.

Jacqueline Lowry, new tenant

Building performance

Designed energy performance

Airtightness n₅₀ (≤ 0.6ACH @ 50 Pa)

0.6 @ 50 Pa

Space Heating Demand (≤ 15 kWh/m².a)

14.05 kWh/m².a

Heating Load (≤ 10 W/m²)

10.45 W/m²

Primary Energy Demand (≤ 120 kWh/m².a)

59.6 kWh/m².a

Primary Energy Renewable (PER) Demand (≤ 60 kWh/m².a*)

46.48 kWh/m².a

Primary Energy Renewable Generation

46.27 kWh/m².a

*+/-15 kWh/m².a allowance if offset by energy generation. See Passivhaus criteria.

Sunningdale Gardens Monitoring data Jan - June 2025. Image credit: Shane Colclough - Energy Expertise Ltd

Services

Heating & ventilation: An integrated heating and ventilation system was chosen, which provided ventilation via the mechanical heat recovery ventilation unit and the domestic hot water and space heating via the integrated heat pump and an integrated immersion heater. External wall mounted panel radiators were installed as back up for space heating in the habitable rooms and 200W underfloor heating mats were specified for the wet rooms.

Summer comfort: The building orientation and location, as well as size and specification of glazed areas, were carefully considered and planned.

Renewables: Solar PV were specified for the roofs.

The Passivhaus standard has been in existence for over twenty-five years and is a tried and tested method of achieving low energy, comfortable housing that easily meets the requirements for nZEB. It’s a quality assurance process that ensures that the houses have been designed and constructed to the rigorous Passivhaus standard and through the attainment of the certification it’s demonstrable proof of the dwelling’s performance.

Sharon Poots Architect, Northern Ireland Housing Executive

Challenges & lessons learned

Non Passivhaus-related challenges: As this is the first time that the NIHE had directly built in 25 years, there were many challenges that the very small design team had to overcome as there was no point of reference and also rather limited internal resources. This meant it was necessary to outsource many of the specialist roles for the project including M&E design and Passivhaus Designer.

MMC supply chain limitations: There were limited MMC providers locally. The project team tried to specify island-based providers only, to reduce embodied carbon. However this limited the experience and the choices open to the project team, for example there were only 2 manufacturers of aerated blocks on the island of Ireland.

Procurement: Procuring the team under the overarching Pagabo framework worked well and simplified the process of appointment. The limited expertise in the areas of MMC and Passivhaus meant that thiere was a short and select list. A well-structured questionnaire aided the selection process, as did the decision to place quality above cost in the tender evaluation.

Passivhaus quality assurance: The project team found that working towards the attainment of the Passivhaus certified standard worked well in terms of reducing the performance gap and meeting the airtightness requirement.

Post-occupancy monitoring: The Sunningdale Gardens properties an are all being monitored by Energy Expertise Ltd in association with Ulster University, to provide independent monitoring and assessment of the performance of the dwellings, focusing on indoor air quality, energy consumption and occupant satisfaction. By monitoring the energy consumed for heating and lighting over a 16 month period, a figure will be available to compare the actual regulated load energy consumption with that predicted by the SAP software, used to produce the Energy Performance Certificate (EPC). From the already-commenced post pccupancy monitoring, NIHE is reporting benefits of improved energy efficiency, lower heating bills, comfortable and healthy indoor environments for occupants, and wider societal benefits of improved health and well-being for occupants.

Architect’s view

The Sunningdale Gardens project has come following years of compiling business cases to attain multiple Government departmental approval in order for NIHE to gain permission to build again. The brief was to provide much needed social housing stock to help address the urgent housing need, to pilot MMC and to build to Passivhaus Standard so as to provide an exemplar pilot for other social housing providers, through our role as Home Energy Conservation Authority for NI (HECA).

The origin of this project lies in the common interest of the Housing Executive and the Department for Communities to explore the viability of Modern Methods of Construction (MMC) as a means of helping to increase the supply of social housing in Northern Ireland. The business case has been submitted specifically in response to both DfC’s request and the NIHE’s Business Plan KPI that has been agreed with DfC that the Housing Executive (Landlord side) undertakes a pilot project to assess MMC as a suitable model for future social new build in Northern Ireland.

It was realised through the undertaking of a feasibility study which involved local providers of MMC that the building performance is comparable with traditional builds with the added opportunity to provide improved thermal performance, airtightness, weather tightness and a generally better execution. Also with the ever-increasing focus on climate change, carbon emissions and energy use, it was subsequently agreed with the Department that a MMC project would also offer the opportunity to explore the viability of combining energy efficiency measures with MMC construction, and that this could possibly serve as an exemplar for a model of future social housing construction. It was decided that the pilot project would be designed and certified to Passivhaus standard so as to ensure the performance was attained as per the brief.

Sharon Poots, Architect, Northern Ireland Housing Executive