Building Performance Analysis + Climate-Responsive Design
Interrogating an Existing Architectural Proposal
How can an architectural design be developed further to improve energy efficiency, reduce overheating risk and respond to a changing climate?
At Oldham Common, we were appointed by a client who had already commissioned an architectural design from another practice. Although the overall proposal had been established, the client wanted to investigate whether the construction fabric, glazing and solar-control strategy could be improved to deliver a more energy-efficient and comfortable home.
Our involvement focused on assessing the existing design through the Passive House Planning Package (PHPP), using the findings to inform further development of the building envelope and solar shading strategy.
Rather than redesigning the architecture from the outset, our objective was to understand how the proposed building would perform and identify where targeted changes could make a meaningful difference.
Reconstructing the Design in Revit
Before undertaking the PHPP assessment, we developed a three-dimensional Revit model using the architectural drawings supplied by the client. The model provided a coordinated representation of the proposed dwelling, allowing us to establish the geometry and extract key information needed for the energy assessment, including building dimensions, envelope areas, glazing arrangements and orientation.
This was an important first step. The accuracy of an energy model depends on the quality of the information used to construct it, and translating the existing drawings into a coordinated three-dimensional model allowed the proposed design to be interrogated systematically. The Revit model subsequently provided the basis for evaluating alternative building-performance strategies through PHPP.
Evaluating the Building Fabric
The thermal performance of a dwelling depends heavily on its external envelope. Walls, roofs, floors and glazing all influence the amount of heat transferred between the internal environment and the outside.
We reviewed the proposed construction assemblies alongside the PHPP assessment, considering how insulation specifications and construction build-ups could support the client's energy-performance objectives.
The assessment incorporated the following building-fabric performance values:
Building element | U-value |
External walls | 0.190 W/m²K |
Pitched roof | 0.110 W/m²K |
Flat roof | 0.140 W/m²K |
Ground floor | 0.172 W/m²K |
The findings informed further development of the wall, roof and floor specifications, with revised construction information prepared to reflect the project's thermal-performance requirements.
However, a well-insulated building envelope is only one part of the equation. Reducing unwanted heat loss does not automatically prevent a building from overheating during warmer periods.
This became a central consideration in the Oldham Common assessment.
Understanding the Risk of Overheating
High-performance glazing can improve thermal efficiency, but windows also admit solar radiation into a building. Depending on their orientation, area and shading, this solar gain can contribute to elevated internal temperatures during summer.
For Oldham Common, we investigated the relationship between glazing specification, window sizes and external shading, with particular attention to how the dwelling might perform under warmer summer conditions. The PHPP model incorporated high-performance triple glazing, with products considered from Internorm and Fakro. The assessment also examined external shading to roof windows and larger glazed openings.
Rather than evaluating the proposal against current climatic conditions alone, we explored how its performance might change as summer temperatures increase.
Testing Future Climate Scenarios
Three summer climate scenarios were considered:
Scenario 1 - Standard climate: The project's standard PHPP climate data.
Sencario 2 - +2°C summer: An adjusted scenario representing a two-degree increase in summer temperatures.
Scenario 3 - +4°C summer: A more demanding scenario representing a four-degree increase in summer temperatures.
These scenarios were used as comparative stress tests to understand the sensitivity of the proposed design to warmer conditions, rather than as precise predictions of future weather. The assessment measured overheating frequency using the proportion of time that indoor temperatures exceeded 25°C, with the PHPP report adopting a threshold of less than 10% as the benchmark for acceptable overheating performance.
Three Approaches to Solar Control
To understand how the building might be improved, we assessed three alternative design strategies.
Scheme 1 — Initial Shading Strategy
The first assessed scheme incorporated external awning-style shading to most pitched-roof windows and a pergola-style slatted timber arrangement above the principal glazed opening.
Under the standard climate scenario, the model indicated an overheating frequency of just 3.2%.
However, this increased to 14.9% under the +2°C summer scenario and 27.5% under the +4°C scenario. Although the scheme performed acceptably under the standard climate assumptions, the results highlighted its vulnerability to warmer summer conditions.
Scheme 2 — Enhanced External Shading
The second scheme retained the principal building envelope, window sizes and glazing specification while introducing more effective solar shading.
The pergola-style arrangement was replaced with a solid shading device, and additional external awnings were considered for roof windows, including the flat-roof glazing.
The improvements were substantial.
Overheating frequency fell to 0% under standard conditions and 2.0% under the +2°C scenario. Under the more demanding +4°C scenario, however, the result remained at 13.1%, above the assessment's 10% benchmark.
This demonstrated that relatively targeted shading interventions could significantly improve summer comfort without fundamentally changing the architectural design.
Scheme 3 — Enhanced Shading and Reduced Glazing
The third scheme investigated whether further improvements could be achieved by combining enhanced external shading with selective reductions in glazing area.
The tested changes included removing two roof windows, reducing the width of selected rooflights, narrowing the principal glazed opening and reducing the size of the flat-roof lantern.
This produced the strongest overheating results across all three climate scenarios.
Under standard and +2°C summer conditions, the predicted overheating frequency was 0%. Even under the +4°C scenario, the result was reduced to 9.4%, falling below the benchmark adopted in the report.
The findings demonstrated the potential value of combining effective shading with carefully considered glazing proportions.
Balancing Thermal Performance and Architectural Quality
The analysis also highlighted an important design consideration: reducing glazing area may improve summer comfort, but it can also affect daylight, views and the quality of internal spaces.
The most thermally robust option is not necessarily the most appropriate architectural solution in every respect.
For example, reducing the size of a roof lantern could affect daylight penetration into deeper living areas, while smaller adjustments to other windows might offer a more acceptable balance between comfort and architectural quality. The PHPP results therefore provided a basis for informed design decisions rather than prescribing a single solution.
By comparing the three strategies, we were able to demonstrate the implications of different interventions and give the client a clearer understanding of the available options.
From Analysis to Construction Information
The assessment informed subsequent refinement of the proposed building fabric, including the construction specifications for the walls, roofs and ground floor. Detailed Revit drawings were developed to communicate the construction build-ups and thermal requirements, translating the performance considerations into architectural information that could support further technical development.
This connection between analysis and detailing was an important part of the process. Energy modelling is most valuable when its findings influence real design decisions, rather than remaining a separate exercise undertaken after the architecture has been resolved. The principal deliverable to the client was a PHPP report documenting the design assumptions, climate scenarios, alternative strategies and overheating results.
Designing for a Changing Climate
Oldham Common demonstrates the value of interrogating an established architectural proposal through building performance analysis.
The initial assessed shading strategy appeared acceptable under standard climate conditions, but its performance deteriorated considerably when warmer summer scenarios were introduced. Further testing showed that improved external shading, combined where appropriate with selective glazing reductions, could substantially reduce this risk.
The exercise also informed the development of the building fabric and its associated technical specifications.
Ultimately, the project illustrates how Revit-based modelling, PHPP analysis and architectural detailing can work together to support more informed design decisions.
A building designed to perform efficiently today should also be considered in the context of the climate it may experience throughout its lifetime.
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