Homeowner and lecturer in Sustainable Architecture, Dr Stephen Finnegan is rising to the challenge of achieving a Net Zero Carbon (NZC) Victorian home in a leafy suburb of Liverpool. His objective is to minimise running costs, emit no carbon emissions in operation and run the entire property on electricity, largely generated through sustainable sources.
Here, we take a look at the project.
The house, a large detached, brick-built property constructed at the turn on the 19th Century, is typical of the style of building of the period. Solid walls, high ceilings, a walk-in cellar and occupied roof rooms (historically used as servants quarters!). Heating the four-story property had originally been via open, coal fires in every room, including those in the roof prior to the installation of gas central heating.
Dr Stephen Finnegan, who is a lecturer in sustainable architecture at the University of Liverpool, plans to take the building back to a bare shell and incorporate as many energy harvesting and low energy consumption systems as is practical in the restoration of the house. He will then carefully monitor energy and carbon usage with the overall target of Net Zero Carbon emissions.
His ultimate objective is to run the house entirely on electrical energy, through the incorporation of a solar PV system with a SunSynk battery storage system, an Air Source Heat Pump (ASHP), thermal store and monitoring kit (all of which will be provided by Dynamis Associates Ltd). This retrofit system will provide domestic hot water and underfloor space heating. An electric vehicle charging point and a ‘time in use energy tariff’ will catapult the house into the 21st Century.
Fabric “first approach” to thermal performance.
According to Dr Finnegan, it is well established that around 20% of UK carbon emissions are generated through heating, hot water and cooking in domestic properties. With over 60% of current housing stock built pre-1960 when little thought was given to heat-loss prevention, the challenge of reducing these emissions is significant.
New-build properties can be built to far more thermally efficient standards than their predecessors, so the Government’s target of slashing overall carbon emissions by 78% by 2035 puts real focus on older buildings where retro-fitting of heat loss prevention methods and reducing energy inputs, particularly of carbon rich sources such as gas, are so crucial.
In older properties, particularly like this house, built over 120 years ago, when energy costs were far lower and measures to prevent heat-loss through walls and roof were rarely considered, the challenge is even greater.
Dr Finnegan explains.
“Our first big obstacle to overcome is heat loss prevention and this primarily focusses on improving insulation and air tightness”
Up to 40% of a building’s heat loss can be attributed to air leakage , so it is vital that air tightness is included in any programme of measures designed to improve a building’s thermal performance. A so called ‘fabric first’ approach.
A breathable, sealed-box environment.
Traditional insulation materials such as mineral wool or rigid board products can be time-consuming and expensive to retrofit and if not installed correctly can still lead to air leakage. It is almost impossible to achieve a completely airtight seal, whilst still allowing the building to breathe naturally.
“We needed a more efficient, modern method of insulation that provides a high level of thermal insulation and help us create a sealed ‘breathable’ box environment to give us better management of both heat input and ventilation. Electricity is already expensive and prices will only go upwards, so it’s vital that we do all we can to first minimise consumption, prior to the installation of any renewable energy technologies.”
Early on in the restoration programme, insulation specialists, Green Horizon Energy Solutions were brought in to advise on how best to minimise thermal loss. Director, Matt Lawford recommended the use of Foam Lite LDC 50, a breathable, spray applied ‘open cell’ insulation system from Huntsman Building Solutions .
Matt Lawford explained,
“Huntsman’s Foam Lite is a spray applied insulation system that expands quickly but gently, sealing all gaps, service holes and hard to reach spaces, virtually eliminating cold bridging and air leakage.”
“As well as the entire roof area, we recommended applying spray foam insulation to the underfloor area of the timber ground floor. Up to 20% of heat can be lost through an un-insulated suspended floor and, with easy access from the cellar area, this gave us a quick-win in terms of heat loss mitigation.”
Spray applied, open-cell insulation.
Unlike the urethane foams of 20 years ago, modern spray foams such as Huntsman Building Solutions Foam Lite LDC 50 uses water as the blowing agent. This means that the reaction between the two components produces a small amount of CO2 which causes the foam to expand. Cells of the foam burst and the CO2 is replaced by air.
This “open cell” foam provides outstanding insulation properties but still allows the building to breathe naturally, without the risk of condensation. HBS spray foam insulation systems were developed in Canada to cope with their severe winters and are now widely used in UK in both the residential and commercial sectors.
In the roof area, the original lath and plaster covering was removed from the underside to the pitched roof and 50mm section timber counter-battens installed. The roof had been re-slated in the 1960’s and the bituminous sarking felt covering was found to be in sound condition so no further remedial work was needed.
A thin layer of glass fibre was removed and HBS Foam Lite LDC 50 insulation sprayed directly on to the exposed felt to a depth of 120mm. After trimming flush, the ceiling was fitted with a Vapour Control Layer (VCL), re-boarded and skimmed.
With good access to the underfloor at ground level (via the basement), insulation was sprayed between the flooring joists to a depth of 120mm, eliminating draught incursion to the rooms above.
Post restoration data collection
The house restoration project began in early 2021 with a target for completion and occupation by the end of the year. An array of temperature, energy and relative humidity sensors are being installed as work progresses allowing a comprehensive programme of data collection covering air tightness, net electrical energy consumption, thermal performance and so on. These will be collated into a formal paper to be published by Dr Finnegan during the latter part of 2022. Alongside a live data feed open to the public and hosted by the Zero Carbon Research Institute www.zcri.co.uk. Which was founded by Dr Finnegan.
Learn more about Huntsman Building solutions: www.huntsmanbuildingsolutions.co.uk