Building Physics - Design Guidelines

The design phase of a building is crucial in shaping its energy performance and overall comfort. Key considerations in building physics, such as minimizing heat losses, optimizing solar gains, and managing internal loads, play a pivotal role in determining energy requirements and long-term efficiency. This article explores practical design guidelines that planners can follow to improve building performance.

Minimizing Transmission Heat Losses (QT): Transmission heat losses occur through the building envelope, and reducing them is essential for energy-efficient construction. A compact building structure is ideal, as it minimizes the envelope surface area relative to the heated volume. This concept is expressed by the A/V ratio (enveloping surface area to heated volume ratio). A lower A/V ratio leads to reduced transmission losses and improved energy balance.

Key building envelope components to consider include:

• Floors

• Walls

• Roofs

• Doors and windows

• Thermal bridges

By addressing these components, planners can reduce heat losses and design details that minimize thermal bridging using standard, proven solutions.

Minimizing Ventilation Heat Losses (QV): Airtightness is critical for energy-optimized buildings, as it directly impacts ventilation heat losses. Detailed planning is required to ensure airtightness across all construction trades, with careful implementation and final inspections like blower door tests to verify quality.

Important factors include:

• Building airtightness: Detailed planning for airtight construction

• Ventilation strategy: Use of controlled ventilation with heat recovery systems to enhance efficiency

• Building exposure: Optimize natural ventilation and air circulation while minimizing unwanted air leakage

Optimizing Solar Gains (QS): Solar gains contribute to a building's heating load in colder months but can lead to overheating in summer. Balancing solar gains with the risk of summer overheating is essential, particularly in non-residential buildings. External sun protection, optimized window orientation, and specific glass properties can help manage solar heat gain throughout the year.

Key aspects of window design include:

• Glass area

• Orientation: Maximize solar gain in winter and minimize it in summer

• Glass specifications: Use glazing with low U-values to improve insulation

• Shading systems: Install external shading to manage summer heat

Utilizing Internal Gains (QI): Internal heat gains come from occupants, appliances, lighting, and equipment, particularly in non-residential buildings where higher occupancy and equipment densities result in significant internal heat generation. Optimizing internal gains during winter can help reduce heating needs, but excessive internal gains during summer can lead to overheating.

For residential buildings, internal gains are typically calculated based on:

• Occupant numbers

• Appliances such as refrigerators, stoves, and lighting

For non-residential buildings, internal gains are often calculated individually, but standard profiles exist for specific building types like offices and hospitals.

Designing energy-efficient buildings requires a holistic approach to managing heat losses, solar gains, and internal heat loads. By optimizing these factors during the planning phase, designers can reduce energy demand, improve comfort, and enhance overall building performance. Following these guidelines ensures that both residential and non-residential buildings are well-prepared for a sustainable, energy-efficient future.