With the upcoming launch of RdSAP 10 in early 2025, Domestic Energy Assessors (DEAs) will soon have the option to include air pressure testing results in Energy Performance Certificates (EPCs). This small change could have a big impact, offering homeowners and assessors a more accurate reflection of a property’s energy efficiency and potentially leading to better EPC scores.
What Is Air Pressure Testing?
Air pressure testing measures how much air leaks out of a building through gaps in windows, doors, walls, and other areas. The test results in an “Air Permeability Score”—the higher the score, the more air is escaping. This is important because air leaks make it harder to keep a building warm, which can lead to higher energy bills and increased carbon emissions. The test follows CIBSE TM23 standards, which cover both residential and commercial buildings.
There are two main methods used for testing:
### The Two Types of Air Pressure Testing
1. **Blower Door Test**
In a Blower Door test, a fan is mounted to an external door, and the rest of the openings are sealed. The fan creates a pressure difference, and as external air flows through cracks and gaps, the test calculates the building’s airtightness. The result is called “AP50,” which measures air permeability in cubic meters per square meter per hour at 50 Pascal (m³/m²/hr @50Pa). This test is quite common and can be done while the building is still occupied, although it’s important not to close internal doors or open windows during the test.
2. **Pulse Test**
The Pulse test is newer, having been introduced in 2022. A device is placed in the center of the property, and it releases a known amount of air into the building. The test then measures how the air pressure inside responds, factoring in temperature and ambient conditions. Like the Blower Door test, occupants can stay in the building, but they’ll need to keep doors open and windows closed during the test.
Why It’s Beneficial for Homeowners
For homeowners, including air pressure test results in RdSAP 10 means a more accurate EPC score. Since the test shows how much air is leaking from a property, it helps assessors determine how well the property is retaining heat and managing energy. A lower air permeability score (meaning less air leakage) could lead to a higher EPC rating. This is especially helpful when selling or renting a property, as it gives a clearer picture of its energy efficiency.
Additionally, homeowners can use the results to pinpoint areas that might need improvement—like sealing gaps around windows or doors—to boost their energy efficiency and save on heating costs in the long run.
What Thermcal Ltd Thinks
Gareth Chambers, Technical Director at Thermcal Ltd, is excited about the changes in RdSAP 10. He says, “We’re thrilled that air pressure testing is being added to RdSAP 10. This will give homeowners and assessors the opportunity to get a more accurate EPC score. At Thermcal, we often get questions from homeowners wondering why their RdSAP EPC is lower than a new build’s EPC. One common reason is that air pressure test results aren’t included. RdSAP assumes a score of 15, which is the worst-case scenario. A better result might be around 3 or 4. By adding air pressure testing, homeowners will have a chance to improve their EPC scores and better understand their home’s energy efficiency.”
Conclusion
The introduction of air pressure testing into RdSAP 10 offers a valuable opportunity for homeowners and assessors to get a more accurate picture of a property’s energy performance. While not required, air pressure testing can help increase EPC scores, potentially leading to better energy efficiency and lower bills. Homeowners will be able to make more informed decisions about how to improve their homes, whether it’s through simple upgrades like sealing air leaks or making larger energy-saving improvements. It’s a small change, but one that can make a big difference in how we assess and improve energy efficiency in our homes.




