New Part L Revision re Applications lodged after Nov 2011

The URL of the page on the RIAI website from which the above notifation is take is –

http://www.riai.ie/index.php/news/article/revised_part_l_-_important_message_from_the_riai_practice_director/

@onq wrote:

I cannot help feel that this Part L has been let run away with itself with no real assessment of its implications.

Far too much of the billing and cooing on Construct Ireland seems to be without critical comment – nothing is THAT good.

a working understanding of the current part L makes it much easier to understand what is coming down the tracks.
Basicaly, houses are going to go from 40% more efficient than the baseline standard, to 60% more efficient.

this is going to to put much more focus onto the dark art of thermal bridge calculations, energy demand calculations and air tightness detailing.

the days of worrying about elemental u values are well behind us.

I don’t disagree with anything you say Henno, but there is a wider picture than the aspirations of people who seem to centre on thermal efficiency and sealing.

People I have spoken to have agreed that the sealing standard is pointlessly high may be leading us to serious ill bronchial ill health.
Sensationalist as this sounds it is clear that we have assimilated aspects of commercial design with none of the safeguards.

MVHR is a cut down version of full air conditioning but with none of the fire prevention measures.
In addition the hazard is higher in the house which has potentially a 100% sleeping occupancy.

This is greater than even a hospital or nursing home where there are alert staff on call.
Branching ducts can allow for the regulated transfer of old smoke and fumes transfer.

Ducts containing water and deposits can be a breeding ground for bacteria.
This can create conditions for legionella to grow outside of the hot tub.
http://www.cmse.ie/blog/legionella-in-ireland/

I don’t think we’ve thought this all through for Irish conditions.

To compound matters, we live in a wet climate, rather than a central European dry climate. Without climatic control on venting systems moist air is delivered from the outside directly to the middle of the house.

Also please note that the mean temperature due to Global Warming is climbing. During warmer spells such as at the moment or more particularly during the summer what happens when the house overheats? You open the window thus bypassing the air tightness requirements.

Air tightness is a black box physics experiment that works when you do not include the variable; people.

Importance of Ventilation

http://www.humidex.ca/humidexwp/wp-content/uploads/2010/12/ASHRAE-NOV-2010-IAQ-in-AirTight-Homes.pdf

“What we must always remember is that buildings are for people, and thus health must trump energy. When concerns for energy costs exist because of cold or hot climatic conditions, the response should not be to reduce the outdoor air ventilation, but rather to pursue energy conservation measures. Similarly, when concerns are present for high outdoor air contaminant concentrations, then air cleaning measures should be pursued. The home ventilation mantra remains; build tight, but ventilate
right.”

This is what it all comes back to Shadow – the climate of thsi country and what is reasonable

This started with a concern about saving fuel and reducing the carbon footprint.

Then it progressed through a reasonable level of insulation.

Then it went mad with sealing and ventilation.

Ventilation that isn’t entirely passive requires energy to drive the pumps.

Pumps need to be replaced every seven to ten years at considerable cost and expense.

Someone needs to to a proper accounting of costs and savings overall for the benefit of the consumer – us!

Here’s a great detail – a construction stuffed full of insulation – http://t.co/v8d1Hcx1

100 Interweb points for guessing where the interstitial condensation is most likely to occur.

Hint condensation that occurs within the insulation can reduce its effectiveness.

There is a theoretical point beyond which insulation cannot go.

Thus the emphasis on sealing, but its not understood.

Unless you seal the sandwich perfectly it starts to get wet internally.

Realizing this was impossible the powers that be suggested controlling “air quality”.

People get confused between oxygen levels and humidity levels, both of which need control for “good air”.

@onq wrote:

MVHR is a cut down version of full air conditioning but with none of the fire prevention measures.
In addition the hazard is higher in the house which has potentially a 100% sleeping occupancy.
.

on this issue i completely agree with you. all my specifications for hrv include smoke protection collars for all ducting when passing through floors / walls. Also, connection to fire detection system is a must to allow for full ‘shut down’ in case of fire.
These were issues brough to the attention of BRAB, but no mention in Part L 2011. We can only hope for main stream provision in an altered Part B…. but regardless we as designers must provide the best spec we can .

@onq wrote:

Ducts containing water and deposits can be a breeding ground for bacteria.
This can create conditions for legionella to grow outside of the hot tub.
http://www.cmse.ie/blog/legionella-in-ireland/

I don’t think we’ve thought this all through for Irish conditions.

in this i dont agree. again, care needs to be taken with the specification ie never flexible ducting!! and always locate the system within the heated insulation envelope.
The exhaust air never actually mixes with the incoming air, therefore there is no influx of contaminated air back into the house… if anything the hrv system works as an efficient exhaust vent system. the temps required to allow legionella wont be reached in the exhaust system as long as common sense prevails with condensation issues.

@onq wrote:

Here’s a great detail – a construction stuffed full of insulation – http://t.co/v8d1Hcx1

100 Interweb points for guessing where the interstitial condensation is most likely to occur.

Hint condensation that occurs within the insulation can reduce its effectiveness.

There is a theoretical point beyond which insulation cannot go.

Thus the emphasis on sealing, but its not understood.

Unless you seal the sandwich perfectly it starts to get wet internally.

Realizing this was impossible the powers that be suggested controlling “air quality”.

People get confused between oxygen levels and humidity levels, both of which need control for “good air”.

you picked a very bad example to make your point

that detail, while not perfect… is specifially designed to reduce thermal bridging as much as possible. the roof construction is created as a warm roof type (see gutex wood fibre) with a breathable felt over. In this construction vapour will only condense into liquid over the felt and into a ventilation layer and exhausted away. the dew point in this detail occurs outside the insulation layer
condensation in the wall construction will occur at the cold face of the cavity insulation, and is allowed to exhaust through the external blockwork.

Investigations into the condensation point can be done with software such as wufi, which gives a dynamic rather than static view of where condensation will occur.

Henno,

How can you be so sure where the dewpoint will fall?

It is a function mapping the reduction in temperature against humidity.

The more insulation there is the greater the chance that dewpoint will occur withing the insulation.

I’m not interested in where it *can* occur, but where it will occur with higher insulation for a wide range of conditions.

@henno wrote:

in this i dont agree.

again, care needs to be taken with the specification ie never flexible ducting!! and always locate the system within the heated insulation envelope.
The exhaust air never actually mixes with the incoming air, therefore there is no influx of contaminated air back into the house… if anything the hrv system works as an efficient exhaust vent system. the temps required to allow legionella wont be reached in the exhaust system as long as common sense prevails with condensation issues.

The temp will be exceeded in the input system, with temperature losses from the travel down the pipe and 16-18 degrees required its well within the legionella comfort zone, and legionella is only one possible biological outcome when you’re in the 18-24 degree range: that’s where a lot of moulds thrive as well.

thats why they have condensors fitted in the heat exchanger.

Sounds interesting. What do you think they do – Inlet and Outlet? And to the carbon footprint?

are you seriously asking me what do i think a “condensor” does? ……….. :wtf:

Just as a matter of interest;

Post occupancy, what happens when the owner/occupier puts up shelves, pictures, flat TVs, curtains or new lights on various walls. Surely the perfectly assmbled, detailed and airtight proofed environment is compromised. Worse still because of the semi pressurised environment any compromise will focus the movement of vapour to a critically vulnerable location in the wall system.

@shadow wrote:

Just as a matter of interest;

Post occupancy, what happens when the owner/occupier puts up shelves, pictures, flat TVs, curtains or new lights on various walls. Surely the perfectly assmbled, detailed and airtight proofed environment is compromised. Worse still because of the semi pressurised environment any compromise will focus the movement of vapour to a critically vulnerable location in the wall system.

this isnt so much an issue with a masonry house, as the plaster layer is the airtightness layer. simple eduction to the occupier as to how best finish drill holes would suffice ie plenty of caulk

in a TF house it can be an issue but one that should be designed to minimise any risk of puncturing the air tighness membrane. this is usually done by incorporating a service cavity of say 75 – 100 mm between the inner face an dthe timber frame. The air tightness membrane is affixed to the frame so there is a depth protection by the service cavity. Also any good TF spec should include a strong OSB inner lining prior to plaster boarding. This can easily act as a ground for most domestic applications. In cases where there is doubt, the spec should be altered to include cementious board.

basically, fore sight and education is required. it would be a very foolish occupier to pay extra for an air tightness strategy and MHRV and then not know how it affects the dwelling.

as for the pressurisation point, i think you put way too much credit into the ability of a HRv system to create pressure differentials.
A simply day like today where it is say 20 degrees internal climate and 4 degress external would create a vast greater pressure differential than any HRV system could. The investigation of condensation issues should be carried out regardless of any percieved differential anyway. Most problems actually occur when there is negative pressure in summer times when its warmer outside thus creating a situation where condensate moisture is drawn back into the building rather than being allowed to exhaust outward. The use of non breathable materials along the inner face is what causes problems in this situation eg drylining with polythene DPMs etc.