Unit A2 2: Environmental Building Performance and Measurement – The Technical Report
Welcome to your complete guide to the A2 2 Technical Report! In this unit, you step into the role of a professional environmental consultant. You will inspect a real, local building, evaluate how environmentally sustainable it is, carry out scientific calculations, and write a formal report proposing realistic improvements (retrofits).
This internal assessment counts for 30% of your total A Level (or 50% of your A2 year). The report has a suggested word guidance of approximately 4,000 words and is carried out under centre-controlled conditions. Don't worry if this sounds like a big project—breaking it down section by section makes it completely manageable!
1. Overview of the Technical Report Structure
A successful engineering report must follow a clear, professional structure. Think of your report as telling a complete story: from what the building looks like today, to how you tested it, to what changes will make it greener tomorrow.
Your report should include the following standard sections:
1. Title Page & Executive Summary: A concise snapshot summarizing the building's current performance, key audit findings, proposed upgrades, and estimated payback.
2. Introduction & Site Profile: A detailed description of the audited building, including its age, floor footprint, occupancy, and basic construction type.
3. Methodology: A clear explanation of all diagnostic testing equipment used, calculation formulas applied, and survey procedures.
4. Audit and Performance Evaluation: A systematic, evidence-based audit evaluating the building against all 9 Categories of the Code for Sustainable Homes (CSH).
5. Technical Improvement Plan / Retrofit Proposals: Practical, feasible recommendations to improve the building's fabric, water usage, waste handling, and renewable energy generation.
6. Cost-Benefit & Payback Analysis: Realistic economic analysis calculating the payback period for each major investment.
7. Conclusion & Appendices: Final closing summary, data tables, floor plans, lux level records, and thermal imaging photographs.
2. The Core Framework: The 9 CSH Categories
The backbone of your technical audit is the Code for Sustainable Homes (CSH) framework. You must assess your chosen building across all nine specific categories:
Memory Tip – Remember the 9 Categories with this Mnemonic:
"Every Warm Morning Sun Warms People's Health, Making Energy"
(Energy, Water, Materials, Surface Water, Waste, Pollution, Health & Wellbeing, Management, Ecology)
Category 1: Energy and \(\text{CO}_2\) Emissions
This category focuses on the thermal envelope and carbon footprint of the dwelling:
• Fabric Energy Efficiency: Examining insulation levels, U-values of walls/roofs/floors, thermal bridging, and air permeability.
• Dwelling Emission Rate (DER) vs. Target Emission Rate (TER): Comparing actual carbon emissions against statutory building benchmarks.
• Low and Zero-Carbon (LZC) Technologies: Investigating suitable renewable energy systems such as Solar Photovoltaics (PV), Solar Thermal, Heat Pumps (air or ground source), and Biomass Boilers.
Category 2: Water
Reducing indoor potable (drinking) water consumption and conserving resources:
• Indoor Water Targets: Measuring and reducing water consumption per person per day using low-flow aerated taps, water-saving shower heads, and dual-flush toilets.
• Rainwater Harvesting & Greywater Recycling: Installing water butts or integrated collection systems to supply water for non-potable uses like toilet flushing and garden irrigation.
Category 3: Materials
Evaluating the environmental impact of the physical building materials:
• The BRE Green Guide to Specification: Selecting materials rated from A+ (lowest environmental impact) down to E (highest environmental impact).
• Embodied Energy & Life Cycle Impact: Assessing the energy consumed during extraction, manufacturing, and transport of materials.
• Responsible Sourcing: Ensuring materials like structural timber are certified by recognized bodies such as the Forest Stewardship Council (FSC).
Category 4: Surface Water Run-off
Managing rainfall to prevent local flooding and reduce stress on public storm drains:
• Sustainable Drainage Systems (SuDS): Implementing permeable paving for driveways, soakaways, swales, and green roofs.
• Flood Risk Mitigation: Ensuring external surfaces allow natural drainage rather than rapid runoff into storm sewers.
Category 5: Waste
Promoting sustainable resource management during occupancy and construction:
• Internal & External Storage: Providing dedicated, easily accessible bins for household sorting (recyclable vs. non-recyclable waste).
• Composting Facilities: Providing dedicated garden composters.
• Site Waste Management Plans (SWMP): Formulating clear strategies to divert waste from landfill during any proposed retrofit works.
Category 6: Pollution
Minimizing atmospheric pollution and global environmental harm:
• Global Warming Potential (GWP): Ensuring all installed insulation materials have a certified GWP < 5 (avoiding harmful blowing agents).
• Nitrogen Oxide (\(\text{NO}_x\)) Emissions: Specifying low-\(\text{NO}_x\) space heating boilers and hot water systems.
Category 7: Health and Wellbeing
Ensuring the building provides a safe, comfortable, and healthy indoor environment:
• Daylighting: Assessing daylight levels and daylight factors in key living and working areas.
• Sound Insulation: Measuring airborne and impact sound reduction through party walls and floors beyond standard Building Regulations.
• Accessibility & Private Space: Incorporating Lifetime Homes accessibility features and adequate private outdoor space.
Category 8: Management
Providing the tools and practices needed for efficient long-term operation:
• Home User Guide: An easy-to-understand manual explaining how heating controls, ventilation, and renewable systems work.
• Considerate Constructors Scheme: Ensuring retrofit contractors operate cleanly, safely, and respectfully.
• Security: Designing doors, windows, and outdoor lighting in line with Secured by Design principles.
Category 9: Ecology
Protecting and enhancing the surrounding natural environment:
• Ecological Value: Protecting existing trees, shrubs, and habitats.
• Biodiversity Enhancement: Adding native plant species, bat boxes, and bird nesting boxes to increase local wildlife value.
Key Takeaway for CSH: You must address all 9 categories. A common pitfall is writing exclusively about solar panels and insulation while forgetting water, waste, pollution, and ecology.
3. Quantitative Calculations & Diagnostic Tools
Your technical report must not be just a descriptive essay; it requires real engineering data and mathematical calculations.
A. Thermal Performance Calculations
1. U-Value Calculation:
The U-value measures the rate of heat transfer through \(1\text{ m}^2\) of a building element for every \(1^\circ\text{C}\) (or \(1\text{ K}\)) temperature difference. The lower the U-value, the better the insulation.
To find the overall U-value, first calculate the total thermal resistance (\(R_{\text{total}}\)):
\(R_{\text{total}} = R_{si} + \sum \frac{d}{k} + R_{se}\)
Where:
• \(R_{si}\) = Internal surface resistance (\(\text{m}^2\text{K/W}\))
• \(R_{se}\) = External surface resistance (\(\text{m}^2\text{K/W}\))
• \(d\) = Thickness of the material layer (in metres, \(\text{m}\))
• \(k\) = Thermal conductivity of the material (\(\text{W/m}\cdot\text{K}\))
Once \(R_{\text{total}}\) is determined, the U-value is simply the inverse:
\(U = \frac{1}{R_{\text{total}}}\)
2. Heat Loss Rate Equation:
To determine the rate of heat escaping through a specific wall, window, or roof element, use the heat loss formula:
\(Q = U \times A \times \Delta T\)
Where:
• \(Q\) = Rate of heat loss in Watts (\(\text{W}\))
• \(U\) = U-value of the building element in \(\text{W}/\text{m}^2\text{K}\)
• \(A\) = Surface area of the element in \(\text{m}^2\)
• \(\Delta T\) = Temperature difference between inside and outside (\(T_{\text{inside}} - T_{\text{outside}}\)) in \(\text{K}\) or \(^\circ\text{C}\)
Analogy: Think of heat like water escaping through a sieve. The U-value is the size of the holes, \(A\) is the size of the sieve, and \(\Delta T\) is the water pressure pushing against it. Lowering the U-value plugs the holes!
B. Diagnostic Building Testing Equipment
• Thermal Imaging (Thermography): Uses infrared cameras to capture surface temperature differences, allowing you to identify hidden insulation voids, cold spots, and thermal bridging (heat escaping through uninsulated structural joints).
• Blower Door Testing (Airtightness): Measures unwanted air leakage. The building is pressurized and depressurized to a pressure difference of \(50\text{ Pa}\). Air permeability is recorded in \(\text{m}^3/(\text{h}\cdot\text{m}^2)\) at \(50\text{ Pa}\).
• Lux Meters (Light Meters): Measures the illuminance (in lux) on working planes and desks to assess whether rooms receive adequate natural daylight.
4. Cost-Benefit & Simple Payback Analysis
Clients do not just want to know if a technology is green; they need to know if it is financially viable. You must calculate the Simple Payback Period for your major retrofit proposals.
\(\text{Payback Period (years)} = \frac{\text{Capital Cost (\pounds)}}{\text{Annual Savings (\pounds/year)}}\)
Step-by-Step Worked Example:
Scenario: A homeowner currently spends \(\text{\pounds}1,600\) per year on heating. Installing high-performance external wall insulation costs \(\text{\pounds}4,800\). The new insulation is calculated to reduce annual heating bills by \(30\%\).
Step 1: Calculate the Annual Savings (\pounds):
\(\text{Annual Savings} = \text{\pounds}1,600 \times 0.30 = \text{\pounds}480\text{ per year}\)
Step 2: Apply the Payback Formula:
\(\text{Payback Period} = \frac{\text{\pounds}4,800}{\text{\pounds}480} = 10\text{ years}\)
Interpretation: The insulation pays for itself completely in \(10\) years. Every year after year 10 represents pure financial savings.
5. Avoiding Common Assessment Pitfalls
Make sure to keep these examiner tips in mind while producing your report:
• Pitfall 1: Writing purely descriptive text. Don't just define what double glazing is—calculate the actual U-values and heat loss rates for your specific building.
• Pitfall 2: Neglecting the non-energy CSH categories. Ensure water consumption, surface water run-off (SuDS), materials (Green Guide), and ecology are fully assessed.
• Pitfall 3: Recommending unrealistic retrofits. Don't propose a massive roof solar PV array without checking roof orientation, structural suitability, or tree shading.
• Pitfall 4: Omitting the economic analysis. Always provide estimated installation capital costs, annual bill savings, and calculated payback periods for your proposed solutions.
Quick Review Summary
• Assessment: A2 Unit 2 is an internally assessed technical report worth 30% of your A Level (~4,000 words max).
• Core Standard: Evaluate the building against all 9 CSH categories (Energy, Water, Materials, Surface Water, Waste, Pollution, Health & Wellbeing, Management, Ecology).
• Calculations to include: Total thermal resistance (\(R_{\text{total}}\)), U-values (\(U = \frac{1}{R_{\text{total}}}\)), rate of heat loss (\(Q = U \times A \times \Delta T\)), and simple payback periods (\(\text{Payback} = \frac{\text{Capital Cost}}{\text{Annual Savings}}\)).
• Testing Tools: Thermography for thermal bridges, Blower Door testing (\(\text{m}^3/(\text{h}\cdot\text{m}^2)\) at \(50\text{ Pa}\)) for air leakage, and Lux meters for daylight analysis.