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Abstract

The global issue of climate change is now readily accepted by most. Buildings contribute 40% of EU emissions, so the need to address mitigation is clear, but changing climate also creates a need for adaptation in buildings. Modelling is an accepted way of estimating the performance of buildings, but issues exist with accuracy and assumptions. This calls for measurements to be made on new build and retrofit homes. However, field measurements can have issues; they are time consuming, expensive, and can also be intrusive. It is for these reasons that the facilities “Salford Energy House” and “Energy House 2.0” were constructed at the University of Salford in the UK. These globally unique facilities allow for full scale homes to be built inside climatic chambers where variables such as temperature, wind, rain, solar radiation, and snow can be replicated, meaning weather conditions experienced by 95% of the worlds populated land mass can be simulated. The chambers are currently home to five structures in total; examining future housing systems, conservatories, window treatments and whole house retrofit scenarios. In this paper we will discuss the design, construction, benefits, limitations, and an overview of research findings from these facilities.

Practical application

This paper provides insights and learnings as to how environmental chambers shall be designed, specified, constructed and commissioned to lead to successful facilities, it gives details on some of the issues that were encountered around the energy performance gap. Also, some key learnings are delivered from the initial rounds of research on ASHP and building fabric that are useful for domestic design engineers.

Keywords

Energy house 2.0 building performance test chambers test facility

Background

This paper provides readers with technical and engineering insight on Energy House 2.0 (EH2) a globally unique research facility based at The University of Salford (UoS), which is in the northwest of the UK, north of the city of Manchester. Details are given on the design approach, construction, and commissioning aspects of this unique facility. The initial findings of research projects carried out in the 2 years since the EH2 facility was opened are outlined.

EH2 was developed following the construction and operation of several building physics related facilities at the University of Salford, these are briefly outlined next. This paper will cover some of the building physics and building performance research facilities at the UoS. These facilities all come under a research group known as Energy House Labs a grouping of 24 academics, engineers, and support staff in the area, as well as four facilities; a thermal measurement lab., a smart metering lab., Energy House and Energy House 2.0.

Building performance is typically done through either standardized test rigs, such as heat flow meters for materials,¹ environmental chambers,² or heating system tests.³ However, there is a need to understand how all the components of a building work together. “Whole-system” testing is typically conducted through field trials,^4–6 which can require long monitoring periods, are expensive, and sometime invasive to occupants.^5,7

Energy House (EH)

The Salford Energy House is a pre-1920s solid-wall end-terrace, reconstructed in 2011 at the University of Salford using reclaimed materials and traditional methods. It sits inside a full-scale environmental chamber capable of controlled and repeatable conditions, including temperatures from −12°C to +30°C (±0.5°C control accuracy), rainfall up to 200 mm/h, wind speeds up to 10 m/s, snow, and fixed-rig solar simulation. The test property is a typical two-bedroom terrace with an adjoining neighbour—representative of around 21% of the UK housing stock and commonly classified as hard-to-treat. The facility enables detailed investigation of retrofit strategies and performance testing of energy-efficiency products. Examples of this research are: Walls:^1,8, Floors,⁹: Whole House Heat Loss,^10,11 Deep Retrofit of existing homes,¹² Heating Controls.¹³

Energy House 2.0 (EH2)

The EH2 project was conceived in 2016 and was a follow on to the Energy House (EH) project. The aim of the work was to build on the academic and commercial success of the previous facility, and to address the following.

• Energy House (EH) has one house that was constructed inside a pre-existing chamber, the property fits in this chamber well but is constrained.

• EH has HVAC systems that represent the northern European climate, a wider range of conditions was needed.

• The building type the EH represents is valid for the UK but masonry is not used globally.

Before the design process of EH2, around 2016 – a review of large-scale test facilities, was carried out and is presented in brief form below:

An overview of large scale test facilities for building physics research was provided as an output of IEA EBC Annex 58,¹⁴ this outlined 19 examples across the globe. However, only one of these (Salford Energy House) was at the full building scale. Below are several examples that formed part of the literature study for the design study for EH2.

• A recent development is the Sense-City climatic chamber in Paris, France, this The Sense-City climatic chamber, constructed in east Paris between January 2016 and May 2017, is a 200-tonne mobile climatic facility with a working volume of 200 m³. It can be repositioned between experimental zones in under 45 minutes, enabling testing under both controlled (simulated) and real outdoor conditions. Each test zone covers 400 m², with one area featuring a reinforced concrete pit to allow basement-level experimentation. Within these zones, Mini-Cities are built and equipped with extensive sensors to monitor the performance of urban materials, air quality, and pollution in water and soil. The chamber can regulate air temperatures from −10°C to +40°C using electric heaters and cooling coils. The ceiling can independently mimic the same temperature range, allowing simulation of day/night and clear/cloudy weather cycles. Relative humidity can be adjusted between 10% and 95%, and simulated rainfall—from light drizzle to storms—can be thermally regulated between +5°C and +30°C. In addition to environmental control, the chamber includes 30 2000 W lamps capable of simulating solar radiation, and it can introduce gaseous pollutants such as CO₂, NO₂, and SO₂¹⁵.

• A non-building physics related, but still highly comparable facility is the McKinley Climatic Laboratory which was established in 1944 to provide controlled cold weather testing for aircraft, as such conditions in the natural environment were unreliable and brief. Located at Eglin Air Force Base in Florida, the main chamber offers a working area of 5100 m² and reaches a height of 21 m at the centre of the hangar. This chamber has a temperature range of −54°C to +74°C. The facility also includes an All-Weather Room, which, although smaller at 91 m², can simulate a wide range of environmental conditions with temperatures ranging from −62°C to +77°C. This room can replicate heavy rainfall up to 380 mm per hour and wind speeds up to 31 m/s, as well as snowfall. Additional testing spaces include a Temperature-Altitude Chamber, capable of simulating altitudes up to 24 km with temperatures between −62°C and +60°C in a 25 m³ space.

• EDF operates a Climatic and Ageing Laboratory in Paris to study the ageing, safety, and reliability of electrical equipment such as pylon insulators and connection equipment. The main climatic room (1200 m³) supports endurance testing under conditions ranging from −40°C to +60°C, including ice and solar radiation tests with a 150 W solar radiation rig. A mobile climatic chamber (26 m³) offers thermal conditioning from −25°C to +60°C. Additionally, an accelerated ageing room (675 m³) simulates severe environmental conditions; rain, heat (up to 50°C), humidity (up to 95%), salt fog, and solar radiation to test ageing, pollution, and solar effects.

EH2 design process and issues

EH2 was designed during the years 2016-2019. Construction on site commenced in February 2020 and was opened in January 2023, with Figure 1 showing the completed building. The following sections describe the chambers and their operation, in conjunction with the research activities.

Figure 1.

(a) Front Elevation. (b) Rear Elevation. (c) Experimental homes inside Chamber 1. (d) HVAC equipment.

Layout

The facility has been designed to construct four modestly sized family homes, using many different types of construction methods and materials. Each chamber is 19.1 m (w) x 20 m (l) x 11.1 m (h) giving a floor area of ∼382 m² and a volume of ∼4240 m³. The maximum height of a structure that can be built is 10.95 m; this is due to the impeding HVAC extract ductwork. The building has a central core that contains offices, control rooms and plant areas, as shown in Figure 2.

Figure 2.

(a) Ground floor plan (b) Section.

Flexibility was a main factor; the chambers have cargo doors (4960 mm wide by 5000 mm high). These accommodate any plant/deliveries. This is the maximum permitted to be moved on the UK motorway network with an escort. This was important as these are often the maximum sizes used for offsite structures, such as framed or volumetric structures.

Structural capability: The test chamber includes a soil pit, replicating typical UK clay soil with a 100 kN/m² load capacity - suitable for most domestic low- to medium-rise buildings. The pits use locally sourced 6N graded soil, offering thermal and structural properties similar to those found in many UK regions.

Fabric

As energy efficiency is a key component of the work in EH2, it was important to attain high levels of energy performance for this project. The building has an EPC of B (26).

The specifics for the chambers only are given in the following section.

Due to the extreme conditions simulated in EH2, for the building to remain efficient low U-values across all heat loss elements were important, having the largest surface wall area, was a prime focus. A cold storage wall (by Kingspan) was used internally, behind this a 685 mm ventilated cavity with composite cladding to the external façade. This build up was chosen due not only to its low U-value, but also its ability to deal with extreme condensation risks, due to the ventilated cavity which allows any interstitial condensation to drain to the outside of the building. The design U-value of the wall is 0.10 W/m²K.

Climate range

A study was carried out to inform and validate the design parameters for the chamber; this focused on temperature and humidity in the main. The position of 7322 cities were taken from the Centre for International Earth Science Information Network at Columbia University in partnership with NASA’s Socioeconomic Data and Applications Centre”.¹⁶ These cities represent a population of 1,943,720,611 (almost two billion) people. Weather data for these cities was generated using Meteonorm.¹⁷ This dataset was used to study the climatic coverage of EH2 systems, as shown in Figure 3.

Figure 3.

Locations with air temperatures within the proposed simulation parameters of −20°C to 40°C above 95% of the time green dots, those between 70% and 95% orange dots and under 70% are red dots.

As shown in A study was carried out to inform and validate the design parameters for the chamber; this focused on temperature and humidity in the main. The position of 7322 cities were taken from the Centre for International Earth Science Information Network at Columbia University in partnership with NASA’s Socioeconomic Data and Applications Centre”.¹⁶ These cities represent a population of 1,943,720,611 (almost two billion) people. Weather data for these cities was generated using Meteonorm.¹⁷ This dataset was used to study the climatic coverage of EH2 systems, as shown in Figure 3. The range of temperatures presented in the design process of −20°C to +40°C to cover a wide range of the densely populated cities across the globe, with a small number of cities being shown in red, mostly in the polar regions.

Solar radiation is a key factor in terms of studying heat gain and overheating in buildings alongside moisture transportation, it is also difficult to repeat in chambers conditions at this scale, infrared radiation was chosen to be the source of heat, lamps were chosen with spectral range as close as possible that of sunlight. These lamps contain two elements to cover a broader spectrum of heat, ranging from 0.5 µm to around 6 µm, with output peak at 1.5 µm¹⁸. This is not a perfect match for natural sunlight typical,¹⁹ in terms of heat delivered by the sun, at ground level, this was the closest match given power requirements, practicality, and cost. The solar lamps are currently mounted on mobile rigs for fenestration overheating experiments. In the future, a rotational robotic arm system will be developed to deliver controlled solar irradiance based on simulated weather and time of day. The climate study found that this setup could replicate solar intensity for 95% of sampled cities, 95% of the time.

Note – Following a developing research area at EH2 on the topic of overheating and extreme climates, in Spring 2025 works were undertaken to the HVAC equipment and controls systems. This work added extra capacity to the heating and cooling systems, allowing the following extended ranges to be met; −23.5°C to +51°C.

Rain can have a significant effect on the performance of a dwelling, with studies on masonry elements finding significant changes in the conductivity of bricks and moisture that should be (but are often not) considered in energy models.²⁰ An array of test rigs was designed and manufactured to allow rainfall rates of up to 200 mm/hr to be projected onto the facades of the test dwellings. This water is chilled to represent the climate in which the chamber is set to. The climate studied indicated that this will deliver conditions found in 94% of cities sampled, 95% of the time.

Snow has an insulating effect on the roofs of buildings, with low density, a low conductivity 0.045 W/mK, it also has a high albedo, with the ability to reflect shortwave radiation, as such is should certainly be a topic of research where possible, especially given the ability to control the rate of fall, thickness etc. To replicate this effect in our test houses, there was a need to produce snow, this is done using a snow machine (Demaclenko eos mm2-kp lance system). This uses compressed air and water forced through a nucleating head, this forms small flakes high up in the chamber that can form larger “snowflakes” as they descend onto the roof of the test houses. Snow can only be made at specific conditions in the chamber (<-12°C and <80% Relative Humidity (RH). The snow in the chambers occurs at very low temperatures where small changes in absolute humidity can have a large impact on relative humidity, resulting in high RH levels during snow tests. The facility has the provision to create around 250 mm of snow per day on the rooftop of the test houses.

Wind has two significant effects on the heat transfer of homes, it can create differentials in air pressures across a structure/building, thus effecting the infiltration heat losses, it can also affect the heat loss of exposes facades such as walls, and roof loss, having the effect of reducing the amount of insulation at the external boundary layer. Studies carried out in the UK on the global heat loss of dwellings under different wind conditions illustrated significant differences in the heat loss over a period.

For this reason, it was crucial for the facility to be able to mimic the effect of wind. However, it is realized that constantly shifting turbulent and laminar flows and random nature of “natural” wind is difficult to replicate. Large scale mobile wind machines are provided with laminar straightening veins that are used to recreate wind on elevations, as shown in Figure 4. They can deliver air velocities of up to ∼17 m/s. This allows the facility to cover 95% of the cities sampled, 95% of the time. Wind driven rain can also be simulated within the chambers; however this is yet to be measured.

Figure 4.

Wind machine at EH2.

HVAC strategy

The building has multiple HVAC systems. In this paper we shall focus entirely on the strategy and plant for the two large chambers. The design requirements laid down by the academic were as follows: -

Heating and cooling to deliver chamber conditions between −20°C and +40°C.

A tolerance of 0.5°C on either side of the temperature setpoint in the chamber.

A maximum stratification of 2°C across the working height of the chamber

The system shall be able to react to dynamic loads in the chamber such as heated/cooled homes, lights, and solar radiation rigs.

Low air velocity system to avoid affecting heat transfer unless added specifically.

Relative Humidity can be controlled between 20 and 80%.

Following a feasibility study of the building, a displacement ventilation system was selected. This allowed for the test chambers to have low velocity air flow, with a design rate of 0.4 m/s. This is fed into the chamber by 2 m high grilled ducts located at ground floor level. This principle relies on gains allowing the air to rise in temperature by around 1-2°C. This forces the warmer and lighter air to rise and is removed from the chamber by ducting mounted on the chamber ceiling. This required a detailed review of the chamber loads, which were as follows.

Solar gains from solar radiation test rigs emitting infrared heating 115 kW.

Chamber lighting 4.5 kW.

Fan gains to air stream of HVAC 24 kW.

Typical fabric and infiltration gain from external 5 kW.

Homes in chamber 45 kW.

This system has several advantages; the extract ducting is at a very high level, reducing the effect on the working height of the chamber, allowing taller structures to be built. This arrangement also allows for a lower supply volume of air at a lower velocity, which aids the research, as unrequired high velocity will cause higher than normal heat loss to the facades. The disadvantage of this system is the requirement of large ground floor grilled ducts, although these do impinge slightly on the working area of the chamber.

The chambers are cooled by two inverter driven ammonia screw compressors. These are equipped with variable speed motors with a range between 1000 and 3600 r/min. These chillers are each rated at 131 kW. Each chiller has a UNISAB three controller to allow for setting and monitoring. The chillers are set up in a duty/duty configuration with a 10% load margin. The chambers are generally each served by one chiller; however, the pipework, pumping and controls allow for two chillers to meet the load of one chamber if needed. The chillers were assigned two separate design loads, low temperature (delivering chilled medium of 27°C to cool chamber to −20°C) and high temperature delivering chilled medium of −5°C to cool chamber to 0°C). These temperatures have associated two separate COP: Low temperature 1.47 and High temperature 2.25. Heat rejection from the screw compressors is delivered through an adiabatic dry cooler. This unit is in a compound external to the building, with louvered panels for acoustic purposes. The unit is a wetted pad system with eight fans.

The chillers deliver Coolflow DTX at 50% concentrate, this is distributed to air handling units (AHU) on the 4^th floor of the building. The medium is pumped to this area using three pumps (duty/duty/standby). These pumps are controlled using an inverter system.

The AHUs are in an internal plant room, located above each chamber. These contain cooling coils through which the medium is circulated, each chamber has three AHU, these are sized to provide 10.67 m³/s giving a total air input volume to the chamber of 32 m³/s. This figure was verified with the assistance of a CFD assessment (details of this can be found later in this article). The AHU works using the displacement principle, with cooler air being supplied at the base of the chamber and warmed air being extracted at the top of the chamber. To maintain specific conditions in the chamber the following features are present in each AHU.

Inlet damper to isolate AHU during defrost cycles.

Cooling coil with drip tray and trace heating – this coil is also used for dehumidification of the air.

Electric heater battery.

Humidifier section with dampened bypass.

The three no AHU recirculate air through the space, the air is provided through one plenum that runs across the top of the chamber and then descends into five no plenums at the base of the chamber around the perimeter of the base of the chamber, this plenum has a perforated grill allowing for air to be discharged evenly across the chamber. Each chamber has a smaller AHU to provide fresh air this allows for air for occupants, combustion air for gas appliances, and positive pressure to the space to reduce infiltration loads. This system delivers 10°C tempered air, this requires the use of the heater battery in the heating season, and non-conditioned during the summer months. This air is filtered and supplied into the return side of only one AHU per chamber. This process can be isolated when the AHU is in defrost mode. The volume of air supplied by this AHU is 264 L/s per chamber.

The design of the chambers and HVAC combination was a process that had no precedent, given that no buildings had been constructed like this previously, with several homes constructed inside of a large, conditioned space. Due to this risk a CFD model was to be created to validate the HVAC strategy. This is detailed below.

Relative Humidity (RH) is a variable that is often required to be controlled and/or stabilised. For instance, when testing air source heat pump performance where RH is can affect the performance especially at lower temperatures.²¹ Two systems exist for humidity control; steam generators are provided to each AHU, to increase humidity levels, whereas dehumidification is carried out using adsorption dehumidifiers (silica gel desiccant wheel type). Two of these units are provided to each chamber with a combined rating of 40.8 kW and throughput of 4800 m³/hr. The regeneration air temp is up to 110°C and is ducted to atmosphere (outside the chamber).

CFD modelling

The modelling exercise was carried out to validate the final HVAC designs before committing to construction. The aims were to examine the performance and distribution of the HVAC ducting arrangements considering the air flows, velocities and temperatures given several variables.

o Empty chambers versus those with homes inside

o Two different air flow rates were examined

o Several different chamber setpoints (−20°C, −10°C, and 4°C)

o Examination of several heat gain sources in the chamber (houses, high-bay lighting and door/floor defrosting equipment)

A CFD model was developed by the consultant Buro Happold, the fabric and HVAC assumptions were taken from the latest design model. A series of assumptions were made about the chamber, the homes inside and other likely gains.

External temperature -

• Lighting gains; as EH2 project has no external windows, artificial light had to be provided, high intensity lighting was required do to the high bay nature of the building, and the laboratory nature. This gain was calculated at 5 W/m²

• Gains from homes; these were based on a typical home sized to AD L1a of the time with occupant and lighting gains, this was modelled as one large house rather than two, for ease of simulation, heated to 18°C, with all associated gain of an occupied house.

• Gains from defrost systems to doors and floors; given the low temperature and moist conditions and the requirement to be able to enter and exit the chamber, heat matts are required to stop the door thresholds freezing closed. These are fitted to all external doorways, but only the large 3 kW matt to the cargo door was considered in the CFD model.

The results of the CFD as shown in Table 1 helped the designers to validate this final stage of the HVAC design process. With minimal temperature disruption delivered by any of the heat generating equipment mentioned above.

Table 1.

CFD models at different chamber setpoint temperatures.

As built performance

Fabric performance was a key metric to the EH2 design team, given the high demand on both heating and cooling, and also to avoid disruption to the chamber operation from external factors.

The most significant heat loss component of the facility is the external wall. This is large section lightly ventilated wall. The internal portion is made from cold store cladding materials, then a 675 mm cavity, and an insulated cladding layer. This was recently evaluated using measurements in accordance with ISO9869,²² these range from 0.05 to 0.10 W/m²K (±14-28%) as detailed by LeHunte.²³ A large variation was due to a ventilated wall, internal convection, and solar gain issues driving convection currents. Overall, the external walls in the facility performed in line with design. These results are presented below in Table 2.

Table 2.

EH2 Chamber wall U-values - Designed and Measured.

	Chamber 1				Chamber 2
Wall	Left	Front	Back	Right	Left	Front	Back	Right
Design U-value¹(W/m²K)	0.097	0.097	0.097	0.097	0.097	0.097	0.097	0.097
Measured U-value (W/m²K)	0.1 (±0.01-0.03)	0.1 (±0.01-0.03)	0.09 (±0.01-0.03)	0.05 (±0.01-0.01)	0.06 (±0.01-0.02)	0.1 (±0.01-0.03)	0.09 (±0.01-0.03)	0.09 (±0.01-0.03)
Difference	+3%	+3%	−7%	−48%	−38%	+3%	−7%	−7%

The chamber pit floors are designed to achieve 0.18 W/m²K, the chamber ceiling 0.10 W/m²K and chamber internal walls, connecting to core of building 0.20 W/m²K.

In large, conditioned chambers, low air permeability of the containing fabric is key, to aid efficiency, increase levels of control and reduce running costs. Air permeability figures were measured using blower door equipment, in line with ATTMA Technical Standard L1²⁴. These are shown in Table 3 and Table 4. These were taken both at completion stage and 28 months later as expected we see a noticeable difference between these figures. There may be several reasons for this. In terms of the chamber, it is likely that some opening up and natural settlement of joints may have taken place over the years, as well as items such as door seals becoming worn and bedded in. In terms of the central core, we see much more pronounced differences between design and measured performance of around 4% at completion stage, and 87% at 28 months. It is thought that this is more likely to be a function of the “sealing up” process involved, as some confusion existed around which ducts, and the like were to be sealed up.²³

Table 3.

EH2 Designed and measured airtightness at completion stage.

	Chamber 1	Central core	Chamber 2
Design air tightness (m³.h⁻¹.m⁻² @50 Pa)	1.5	5	1.5
Measured air tightness at completion stage (m³.h⁻¹.m⁻² @50 Pa)	1.75	4.81	1.39
Percentage increase	17%	−3.8%	−7%

Table 4.

EH2 Designed and measured airtightness after 28 months.

	Chamber 1	Central core	Chamber 2
Design air tightness (m³.h⁻¹.m⁻² @50 Pa)	1.5	5	1.5
Measured air tightness at completion stage (m³.h⁻¹.m⁻² @50 Pa)	2.43	9.34	1.54
Percentage increase	62%	87%	3%

Accuracy of control

When studying buildings in controlled conditions one of the main benefits to be able to closely control the environment. 20 temperature sensors are setup across the chamber to measure the control. These are positioned in a “cross” formation, measuring the front, rear, left, right and centre of the chamber at the heights 2, 4, 6 and 8 m. Not only can this aid with the investigation of measures that only contribute small savings, but also the levels of uncertainty can be reduced. It also allows for repeatable experiments to be carried out. The main design parameter here is to be able to maintain steady/dynamic temperatures within 0.5°C of a given setpoint and for stratification of less than 2°C across the height of the chamber. Figure 5 shows a sample dataset of one of the chambers in, with two full size homes present illustrating stratification of around 0.1°C and a stability of around ±0.3°C.

Figure 5.

24-hour chamber temperature, with temperature sensors (±0.2°C) averaged by height. Note. Dashed lines represent the mean temperature over the 24-h period. 2 m and 4 m are overlayed in the plot dues to close agreement. (a) Time series showing chamber temperature. (b) Density plot highlighting the distribution of temperatures over the 24-h period.

It was necessary for the HVAC systems to be commissioned by the installer prior to test dwellings being built, to demonstrate the design requirements were achieved. Portable shipping containers (with high heat transfer coefficients, to simulate a worst-case scenario house) were added to the chambers, (two containers to each chamber). These represented dwellings and were fitted with electrical heated systems (24 kW) that mimicked a heated home, operating in a time schedule. Environmental testing was also completed in line with the specification mentioned earlier. This simulated all five Köppen-Geiger classifications²⁵ including Adelboden, Switzerland (winter with snowfall), Changi, Singapore, (wet phase of monsoon, with rain, high humidity), and UK (heavy rain, winter temperatures). Testing included steady state and dynamic conditions, ensuring accurate temperature control in maintained with simulated loads, whilst also following a weather profile.

Initial research projects

The paper presents the designed capabilities, systems and control of the Energy House 2.0 test facility, with the measured in use performance of its environmental control systems matching that of its chamber control, and in some cases exceeding. This has allowed for research to commence in the project. Two homes were constructed within the facility to allow for testing to be carried out on low carbon housing for the UK, which focused on the upcoming Future Homes Standard in the UK, which will require new build homes in England and Wales to be built to a nearly zero carbon standard, with high performing fabric and renewable heating systems. The homes are from two large housebuilders/and one manufacturer of homes.

Building fabric performance

Three key studies evaluated the thermal envelope of prototype homes: eHome2, The Future Home (TFH), and the Vector V1 studio.

The eHome2 (Saint-Gobain & Barratt Redrow) baseline report identified a modest 3.9% performance gap between design and measured heat transfer coefficient (HTC), primarily due to discrepancies in roof and wall insulation. Airtightness exceeded expectations, and future interventions such as triple glazing and improved door insulation were recommended to close the gap.²⁶

TFH (Bellway) exhibited a 7.7% performance gap, with roof insulation underperforming by 56%. While wall performance was satisfactory, infiltration heat loss was a significant contributor to the gap, with airtightness 66% worse than design.²⁷

The Vector V1 prototype (Vector Homes), a modular studio home, demonstrated substantial deviations from design specifications. Floor, wall, and ceiling U-values were 217%, 166%, and 67% worse than expected, respectively. Although airtightness was within acceptable limits, the findings prompted a second phase of testing with upgraded materials. It should be noted this was the first property built by Vector Homes, with these key learnings being taken to future designs before building in the real-world.²⁸

A related study explored the insulating effects of snow on flat roofs under extreme conditions. Conducted at Energy House 2.0, the research demonstrated that snow significantly reduced thermal transmission, validating its potential as a passive insulative layer. The findings have implications for energy modelling in polar research facilities.²⁹

A separate study on conservatory performance assessed four ceiling configurations, including glass and polycarbonate with and without the C.H.R.I.S. insulation system. The addition of the C.H.R.I.S. system reduced HTC by up to 30.8% and ceiling U-values by over 79%, confirming its effectiveness in improving thermal performance.³⁰

Heating systems and energy efficiency

A comprehensive evaluation of eight heating system configurations was conducted across the test homes, encompassing air source heat pumps (ASHPs), infrared (IR) panels, underfloor heating, and skirting board systems. Tests were performed under both typical (5°C) and extreme (−5°C) winter conditions, following both a constant and intermittent heating patterns, totalling 28 tests.

IR systems demonstrated rapid heat-up times and minimal stratification but exhibited the lowest system efficiency, particularly under extreme conditions. ASHPs performed reliably, though their efficiency was sensitive to commissioning quality. The study highlighted the need for improved emitter design and installation practices to ensure consistent thermal comfort and energy efficiency.³¹

A focused investigation of the YORK YKF05CNC ASHP in the Vector V1 home revealed optimal performance at 5°C under SAP heating patterns, achieving a Coefficient of Performance (COP) of 3.8. However, the system struggled to meet setpoint temperatures under SAP schedules, suggesting the need for setback temperature strategies.³²

In the domain of domestic hot water (DHW), a comparative study of the Curv and Vaillant systems installed in eHome2 found both systems compliant with BS EN 16,147:2017. The Vaillant system offered greater stability, while the Curv system was more compact and energy-efficient, particularly at higher ambient temperatures.³³

Modelling and optimisation

A multi-objective optimisation study employed a calibrated dynamic thermal simulation (DTS) model of a Future Homes Standard-compliant house. Eight design variables, including U-values, air permeability, and heating setpoints, were evaluated across three scenarios. Results indicated that variable heating setpoints yielded superior optimisation outcomes compared to fixed setpoints. The study underscored the importance of balancing energy efficiency with occupant comfort and demonstrated the value of controlled testing environments in reducing modelling uncertainty.³⁴

Building on these insights, Tsang et al. presents a rigorous calibration methodology for DTS models of two zero-carbon-ready homes - The Future Home and eHome2 - tested in a climate-controlled chamber. By integrating as-built U-values, air permeability, and refined modelling parameters (e.g., roof ventilation, ground temperature, sub-floor voids), the study achieves HTC predictions within 0.5–0.6% of measured values. These results surpass the accuracy of SAP-based models and support the UK’s transition to the Home Energy Model (HEM), reinforcing the value of dynamic simulation in regulatory and design contexts.³⁵

Another study challenged the conventional assumption of a constant HTC. Using experimental data from Energy House 2.0, researchers demonstrated that HTC varies dynamically during heating and cooling cycles. This variability introduces significant uncertainty into performance modelling and suggests that steady-state assumptions may underestimate performance gaps. The authors advocate for incorporating dynamic modelling approaches into regulatory frameworks.³⁶

Renewable integration and innovation

A comparative analysis of solar thermal (ST) and photovoltaic (PV) systems integrated with ASHPs for DHW production was conducted using DesignBuilder simulations of “The Future Home.” Eight scenarios were modelled, varying in system configuration and hot water demand. ST systems delivered more thermal energy than PV systems, particularly under higher demand conditions. The study criticised the Standard Assessment Procedure (SAP) for its fixed demand assumptions, which may underrepresent the benefits of ST systems in regulatory assessments.³⁷

In terms of retrofit innovation, the Thermocill device was evaluated through experimental and computational methods. Installed beneath windows, Thermocill redirects warm air from radiators to reduce heat loss. Results showed a 3-4% reduction in U-values, and the study proposed a standardised methodology for evaluating similar technologies under the SAP framework.³⁸

Summary of current research

The integrated findings from Energy House 2.0 provide robust empirical evidence for improving the energy performance of UK housing. The studies reveal that while many homes meet or exceed design expectations in certain areas, performance gaps persist due to insulation inconsistencies, emitter design flaws, and limitations in current modelling assumptions. The research supports the adoption of dynamic modelling, improved commissioning practices, and innovative retrofit solutions to meet the Future Homes Standard and broader net-zero targets. It was only through the use of the climatic chamber process that these issues could have been found with such closeness of measurement. Future research to be conducted at Energy House 2.0 includes system optimisation, overheating characterisation and mitigation and indoor air quality studies.

Future test houses

As of July 25, research funding has been awarded to build two new homes in Chamber two of EH2. These will be two retrofit based houses, based on 1930s and 1980s archetypal housing.

Conclusion

This paper discusses the capabilities and control of the Energy House 2.0 test facility. The environmental control systems perform as designed, but fabric performance is hindered by air permeability issues, mainly due to assessment and sealing methods in the central core. Chamber airtightness is declining, likely from structural movement and door seal loosening. Despite this, multiple future home prototypes have been rigorously tested, highlighting gaps in fabric performance for timber frame and light gauge steel constructions. Questions also remain about ASHP efficiency outside continuous heating. Complete calibrated datasets for Future Homes Standard homes are now open source, with further heating and DHW system models forthcoming for researchers and industry.

Footnotes

Acknowledgments

The Energy House and EH2 project was funded by the ERDF and the University of Salford, EH2 also had funding from the Office for Students. Both projects had funding from the University of Salford.

ORCID iD

Grant Henshaw

Funding

The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by the Urban Innovative Actions; 2016.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Note

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