Category Archives: PHPP

Air tightness Test-Passive House 0.22ACH

Self Build air tightness test -0.22ach with a volume of 603 m3 @ 50 pascals. 

When one is building to a performance standard the day of reckoning is the airtight test. The reason for this is that when one is pumping fresh air into the house using a Heat Recovery System, rather than relying on simple multiple holes in the wall, it becomes important to control where the fresh air is coming from and where the heat is going.

Airtight Test
Airtight Test

 

 

 

 

 

 

If air is leaking in or out around windows /doors/walls or other gaps in the building fabric then heat is lost and moisture problems in the form of mould can arise or else give rise to damage to the building fabric.

The pressure 50 pascals equates to a 20 mile per hour wind which is not too untypical in Ireland. So if one opts for the Irish  building standard (a minimum standard) this equates to the air in the house changing/leaking 7 times a hour when a wind blows at 20 miles per hour. No wonder people block up the hole in the wall vents .

  • The current Irish building standard  require 7 air changes  per hour (ach) also called leakage at 50 pascals  typically with no heat recovery system As a guidance heat recovery manufactures recommend 3 Air leakages per hour to ensure that the heat recovery system can push fresh air into the house and recover heat leaving the house through its own system rather than through gaps in the building fabric.
  • The passive house standard for a new house requires 0.6 Air changes per hour (ach) at 50 pascals to ensure the heat recovery system works efficiently, ensure that occupants receive the correct amount of fresh air and minimise building fabric damage.

The passive house test differs from the Irish test because it must include pressurisation and depressurisation and use the volume as set out per Vn50 (EN13829).

The Test

Gavin O Shea from Greenbuild was hired for the job.  He is certified/audited by the National Standards Authority of Ireland (NSAI).

The preparation for this entailed sealing all cable ducts and the inlet and outlet pipes for the Heat Recovery System. One also ensures that the shower and sink outlet traps are full of water. The overflow outlet for two water tanks were not sealed off. I did consider a duck valve but it was not in place at the time of the test.

Air Tight Test
Airtight Test

 

 

 

 

 

 

 

 

The test using the Irish method gave a result of 0.181 m3
/(hr.m2).

Gavin O Shea calculated that the equivalent size hole that equates to a result of 0.22 ach is approximately 65.25 cm2 (@50Pa) or a hole 81mm x 81mm if all of the leaks present in the dwelling were concentrated into one hole. That is about a tenth of an A4 sheet of paper.

The results of the air tight test can also help determine the selection of the  Heat Recovery System. If the airtight test is lower then more options are available when selecting a unit.

From my research a passive house standard Heat Recovery Unit will cost more because it needs to be independently tested by the Passive House Institute using their test method. Heat Recovery manufactures have also the burden of putting the unit through national tests or international tests with the end result being the customer pays more.  One has also the option to select a non passive house certified unit for a passive house but when calculating the performance value one needs to account for this in the PHPP software with a 12% reduction below the manufacturers performance claim.

If one wants to view certified Heat Recovery Units one can find and sort them at the following link.  One can see for example at this link the capacity (Column- Air Flow Range) that these units have as it is important to select a unit that is oversized for your particular self build. I would compare it to selecting a mini car to tow a caravan up a hill compared to using a larger car. The small car will struggle from an efficiency and noise point of view while the larger car will be quieter and more efficient at the require flow rates.  I will do a separate post on how I selected our Heat Recovery Unit.

 

 

 

 

 

 

 

 

Performance Standard -Setting the Standard

The passive house software allows one to set your own performance standard by selecting how much energy (oil/gas/electricity) one wants to use to heat the building.

For example current Irish house builds that comply with today’s standard 2014 are estimated to use 100watts per m2 (subjective). The passive house standard if one goes for certification uses 10w per m2 (objective).

The real benefit for using the PHPP software is that the performance approach can be set by the home user. For example if I want to reduce my energy consumption to 1.5 litres of oil per m2 of the house size then I can set the software to a maximum of 15kwh per m2 for the year while maintaining a temperature of 20 degrees Celsius.

In a typical 3 bedroom house with an area of 100m2 the oil usage would be 150 litres a year.  With the PHPP performance software one can set the number of litres of oil (or gas etc) per year that your residential or commercial property will use to within a small margin of error. In other words you select the performance value of your build.

In summary the PHPP software takes into account your comfort and health (temperature and oxygen levels)  by removing high CO2 levels and VOCs and providing an even temperature throughout the house.

A Performance Standard

The Performance Standard

A performance standard is objective (quantitative) . One calculates the energy performance using software called the Passive House Institute planning package (PHPP). It calculates the energy gains and losses. Energy values for example are calculated from the number of people in the house, the solar gain, appliances, all types of losses such as the diameter of copper pipes feeding the hot water taps etc. This tool allows one to create a design for a new build or a renovation where the energy use can be quantified and set by the occupant.

Other solutions for managing building energy usage are in the majority rating systems. A rating system is subjective (nobody knows for sure how efficient it is or how much energy will be used). In Ireland the system is called BER (Building Energy Rating). In England they have BREEAM.

The Irish rating system is weighted towards adding on features such as a porch, solar panels, a heat pump etc., in order to get a high BER rating and it is subjective. One BER assessor may deem it an C2 and another a C3.

The passive house approach primarily aims to reduce and measure your energy consumption and only then do you add features such as solar panels or other heating systems.

While the two approaches exist the BER one is mandatory. What this means is that you could build a house to an energy performance standard that uses the lowest amount of energy in the world and fail to get the current Irish required BER rating.

My interest is the performance approach (using the passive house energy balancing software called PHPP) to design and build the house. As the old/new saying goes “if you can measure it you can manage it“.