Greenbuild | NSAI certified Blower Door Air Tightness Testing, PCN Level 2 Building Thermography

27 July 2023 - Upsy daisy

Extract only ventilation systems tend to be easily validated in the ventilation validation scheme by NSAI. As long as the flow rates meet the minimum requirements, that currently is about the only thing that will give trouble. There is the odd case of no operation or fault light, no ductwork insulation, or as per the previous few notes in this blog, register placement and machine installation, but apart from that, the flow rates are the main concern.

A recent case involved 4 houses that needed the validation procedure to allow closing. 3 of the 4 had the expected flow rates, one of the houses had the expected flowrates in all of the registers, bar one. That one register had a very low flow.

How was that register was allowed to pass the commissioning step? ... well in a way, that is why the validation procedure is being done.

Luckily, the person who did the commissioning was still on site, so together we checked the ductworks, the machine etc; and found this:

Example of vent register where the connection box in the ceiling allows for 2 connections, but only one being used. The other one should have been bunged - but in this case it was not.

If it is not evident, this is a connection box in the ceiling, with 2 connection holes, only one of which is being used (on the right). The other one should have a bung in it, but doesn't, so the planned airflow pathway is much disturbed.

Fortunately, someone with small hands was able to fix a bung even into the connection box, the system was re-balanced and balance was restored.

31 Jan 2023 - 2022 in Airtightness, brief overview

Just for interest: the best and worst tests of the year in 2022

	Best Air Permeability test	Worst Air Permeability tested New build	Worst Air Permeability tested Existing
1	0.285 - timber frame single home	16.38 - new offices, would normally have been expected to be less than 5.	24.44 - offices about to be renovated
2	0.425 - timber frame single home	8.50 - detached block house	15.54 - single home, cold in home survey
3	0.455 - timber frame single home	8.36 - terraced house. A painted airtightness layer was used mainly, but the high test number was due to areas where this layer simply was not present	14.30 - single home, cold in home survey

The three best results are all from the same timber frame supplier. The best we tested that was not from them was q50 of 0.62 m3/hr.m2 on a 2 storey city CLT house.
By the way, where the test is over the allowed limit, there is typically a retest on another day, following rectification works. We do not report on that here.