Building Services and Environmental Performance
Services and performance fundamentals
You must understand the main building services and how they affect performance and defects:
- Heating and ventilation: boilers, heat pumps, MVHR, natural vs mechanical ventilation, and the balance with airtightness.
- Electrical and water services: earthing, RCDs, pipework materials, legionella risk in water systems.
- Environmental performance: U-values, airtightness (air permeability), thermal bridging, overheating risk, and the energy hierarchy (fabric first).
Key concepts:
- Fabric-first approach: reduce demand before adding technology.
- Ventilation–airtightness balance: tighter buildings need designed ventilation to avoid condensation and poor indoor air quality.
- Overheating: solar gain, glazing ratio, shading, thermal mass and purge ventilation.
- Legionella: control by temperature and system design (avoid dead legs, keep hot water hot).
Traps in questions
- Assuming airtightness alone improves performance - without ventilation it worsens moisture and health.
- Confusing thermal mass benefits (summer) with insulation (winter); heavy mass without insulation is not a cure.
- Ignoring cold bridging at junctions, which drives both heat loss and condensation.
- Treating heat pumps as drop-in boiler replacements - flow temperatures and emitter sizing matter.
Worked rule of thumb
Apply the demand–supply–control hierarchy: reduce demand (fabric, glazing, shading), supply efficiently (low-flow-temperature heating, designed ventilation), then control (controls, commissioning). This orders both design and retrofit decisions.
Example: A retrofit that seals a kitchen and removes trickle vents will raise airtightness but cause condensation - restore designed ventilation (e.g., extract or MVHR) alongside the airtightness work.