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What is Alternate-Flow Heat Recovery (AFHR) Ventilation?
Last Updated: 21 August 2025Alternate Flow Heat Recovery Ventilation (AFHR) is an advanced mechanical ventilation system designed to improve indoor air quality while recovering heat from outgoing stale air. It operates by alternating the direction of airflow through a heat exchanger, allowing for efficient heat transfer between incoming and outgoing air streams. This system is particularly effective in reducing...
What is Airtightness?
Last Updated: 21 August 2025Airtightness refers to the extent to which a building’s envelope prevents uncontrolled air leakage between the interior and exterior. It is a critical factor in energy efficiency, thermal comfort, and indoor air quality. In the UK, airtightness is measured in air permeability, expressed as cubic metres of air leakage per hour per square metre of...
What are Airflow Rates?
Last Updated: 21 August 2025Airflow rate refers to the volume of air that moves through a ventilation system, duct, or opening within a specific time period. It is typically measured in litres per second (l/s) or cubic metres per hour (m³/h). This measurement is critical in ensuring effective ventilation, which is essential for maintaining indoor air quality, controlling humidity,...
What is an Airflow Path?
Last Updated: 21 August 2025An airflow path refers to the route or channel through which air moves within a building or ventilation system. It is a critical concept in ensuring effective ventilation, air quality, and thermal comfort in residential and commercial spaces. Properly designed airflow paths facilitate the removal of stale air and the introduction of fresh air, contributing...
What is Airflow?
Last Updated: 21 August 2025Airflow refers to the movement of air in a specific direction, driven by pressure differences, temperature gradients, or mechanical systems. In UK house building, residential retrofits, and home renovations, airflow is crucial for effective ventilation, maintaining indoor air quality, and optimising energy efficiency. Airflow ensures the removal of stale air, control of humidity, and prevention...
What is an Air Source Heat Pump (ASHP)?
Last Updated: 21 August 2025An Air Source Heat Pump (ASHP) is a heating and cooling system that extracts heat from the outside air and transfers it indoors to provide space heating and hot water. It operates efficiently even in cold temperatures, making it a sustainable alternative to traditional fossil fuel-based heating systems. ASHPs are widely used in the UK...
What is Air Purification?
Last Updated: 21 August 2025Air purification refers to the process of removing contaminants, such as dust, pollen, mould spores, volatile organic compounds (VOCs), and other pollutants from indoor air to improve air quality. This is achieved through various technologies and systems designed to filter, neutralise, or eliminate harmful particles and gases. In the UK house building, residential retrofit, home...
What is Air Permeability?
Last Updated: 21 August 2025Air permeability is a measure of how much air leaks through the building envelope (walls, roof, floors, windows, and doors) under a specified pressure difference, typically 50 Pascals (Pa). It is expressed in cubic metres per hour per square metre of envelope area (m³/(h.m²)) at 50 Pa. A lower air permeability value indicates a more...
What is the Air Leakage Rate (A-Value)?
Last Updated: 21 August 2025The Air Leakage Rate, commonly referred to as the A-Value, quantifies the volume of air that can pass through a window frame and its seals under specific pressure conditions. It is expressed in cubic metres per hour per square metre of window area (m³/h·m²) at a standard pressure difference of 50 Pascals (Pa). A lower...
What is the Air Exchange Rate (AER)?
Last Updated: 21 August 2025The air exchange rate (AER) refers to the number of times the air within a defined space, such as a room or building, is replaced with fresh air over a specific period, typically measured in hours. This metric is crucial for assessing indoor air quality and ensuring adequate ventilation in residential and commercial buildings. In...