# Go air tight (eg Q50.3) but forget about MVHR (Mechanical Ventilation Heat Recovery)



## boots (4 Mar 2010)

I hope to start building in the next couple of months.

I had always considered having MVHR but now I'm considering doing away with it and using the saving on achieving a high level of air tightness eg Q50(3).

(I estimate he saving will be approx 10,000 between everything)

Are there any implications on having a house with this level of air tightness which doesn't have MVHR?

Thanks
Boots


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## onq (4 Mar 2010)

*Re: Go air tight but forget about MVHR*

You'll probably suffocate.

ONQ.

[broken link removed]

All advice on AAM is remote from the situation and cannot be relied upon as a defence or support - in and of itself - should legal action be taken.
Competent legal and building professionals should be asked to advise in Real Life with rights to inspect and issue reports on the matters at hand.


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## DBK100 (4 Mar 2010)

*Re: Go air tight but forget about MVHR*

Don't worry, I think ONQ jests.

  You can certainly build to a high level of air-tightness and not use MVHR.
  Just don't rule it out without full and balanced consideration.

  The reason i am confident you won't suffocate is because you are legally required to provide sufficient ventilation under Part F of the Building Regulations.

  The current Part F Technical Guidance can be found here:
http://www.environ.ie/en/TGD/#Individual%20Technical%20Guidance%20Documents

  Means of ventilation. F 1 
  Adequate means of ventilation shall be provided for people in buildings. This shall be achieved by a) limiting the moisture content of the air within the building so that it does not contribute to condensation and mould growth, and b) limiting the concentration of harmful pollutants in the air within the building.
  Table 1 lists the requirements for background and extract ventilation.
  Section 1.2.1.1 states : "In this Subsection guidance is given on approaches to meeting the ventilation objectives as set out in Subsection 1.1 through the use of a) natural ventilation with specific provision for extract ventilation..."
  Section 1.2.2 describes means of providing Natural Ventilation that will comply with the Regulation (F.1).

  The key to any effective ventilation system is *Control.*
  Remarkably in our current Building Regulation Technical Guidance Document Part F, basic Hole-in-The_wall vents with a sliding closing mechanism are still permitted! That is not what I would consider effective - it could barely be considered to be Control.

  The Alternative Systems described in TGD F include:
Passive Stack Ventilation (Chimney / Stack Effect) coupled with an automatic humidity sensitive ventilation inlet control grille. This grille provides a much more effective level of control.

  A French company called ‘Aereco’ makes humidity sensitive on-wall or window frame air inlets.
http://aereco.com/product.php?product=eht
  These devices can also be purchased with acoustic attenuation.
  They replace hit-and-miss vent covers and closeable window vents which have relied on manual control. Effective control is now automatic - responding to humidity to provide ventilation only when required. Heat losses are therefore reduced by limiting ventilation to only when it is required. 
  Humidity is one of the main indicators of the need for air change in the majority of domestic rooms. The vents exploit a property of some fabrics to lengthen when humidity increases in the air and to shorten when the humidity level is lower. Using this principle, polyamide bands in the sensor activate one or more shutters, thus determining the passage of the air according to the ambient relative humidity rate. Units can be set to take into account local conditions and external temperatures.

  Considering again the MVHR system you want to omit, you should firstly think about pros & cons such as:
  - The reduction in ventilation heat losses that can be achieved with MVHR,
  - The capital cost & running cost versus anticipated payback times.
  - Manitenance issues such as filter cleaning and repair costs.
  - The relative lack of good suppliers who are designing & installing these systems to perform at their optimum. They are complex to install and commission.

  If anyone is considering installing a MVHR system it is imperitave that they insist on compliance with Part F of the Regulations and BSEN 13141-7: 2004, Ventilation for buildings, Performance testing of a mechanical supply and exhaust ventilation units (including heat recovery) for mechanical ventilation systems intended for single family dwellings.

In my opinion this means insisting that the supplier / installer provides you with the written test results of your installation demonstrating compliance. If they can't provide that - don't use them.

DBK100
http://www.mesh.ie


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## onq (4 Mar 2010)

*Re: Go air tight but forget about MVHR*

I wasn't really joking.
I have read some of boots other posts.
He appears to be a self-builder, intelligent but inexperienced.
It is precisely to help people like him that I called on the government to produce an integrated set of details for a simple building - like a house - through the RIAI presence in Plan Expo 2009 in November.
The existing approved details are a joke, dealing exclusively with fuel efficiency and sealing - the one showing the blue line running through the junction of the inner block wall with the inner block leaf is priceless.

-----------------------------------------------------

Well done for spotting that the Part F is the new 2009 vintage.
Interesting additional stuff on the MVHR and Passive Stack systems.
Must have a good gander through it before I apply for Registration this month.

I'm claiming the first typo spotted:

_2.1.15 Roofs with a span exceeding 10 m, or
with a *plain* shape other than a simple
rectangle, may require its ventilation to be
increased to 0.6% of the roof area._

"Plain" should read "plan". 

All I can really add is the following:

(i)  there there was a consensus amongst some at the Plan Expo that a hybrid system - designed as passive but with a mechanical assist for certain weather conditions - would be the best of both worlds: economic to run yet providing a full system, and your "bionic" vents were mentioned, IIRC.

(ii) The routing of the ducting design and the location of the air inlets and extracts really need looking at by an expert installer or an M&E Engineer or the air circulation may short circuit leaving dead air pockets in the rooms.

(iii) the OP should also be aware of the need to maintain 30 minutes fire resistance in the 1st floor construction and that this will be compromised by penetrations including:


Recessed downlighters  - seal FR30 hoods to them with fire-seal paste
MVHR penetrations - install fire collars and additional smoke detectors

Good to see the new Part F is out and there are one or two people from whom I should seek comment about it.

ONQ.

[broken link removed]

All advice on AAM is remote from the situation and cannot be relied upon as a defence or support - in and of itself - should legal action be taken.
Competent legal and building professionals should be asked to advise in Real Life with rights to inspect and issue reports on the matters at hand.


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## boots (6 Mar 2010)

*Re: Go air tight but forget about MVHR*

Cheers ONQ for your help.

Most people only build one house in their life, so they're trying to figure it out as they go.Most people I know anyway. 
I'm sure you'ld build a great house, fair play.

Boots


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## onq (6 Mar 2010)

*Re: Go air tight but forget about MVHR*

Boots,

Doctors smoke and architects build houses for others, seldom for themselves.
Self builders need to get their head in the game and take professional advice.
Most don't have the training or experience to tackle a project worth 200K-plus.
Here on AAM we're trying to give them a clue, but the government could do more.
Not moving the goalposts onto another pitch every two years would be a great help.



ONQ.


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## tred (12 Mar 2010)

*Re: Go air tight but forget about MVHR*

what size is your house boots,  i just got quoted in galway, 5400 for a near 3k sq foot dormer for hrv. where u getting ur ten grand out of?.  Its important to consider ventalation of some description, with ur air tight house!


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## onq (13 Mar 2010)

*Re: Go air tight but forget about MVHR*

Tred,

Thanks for your input.

Please could you post with good punctuation and no "text-speak".

Also, re your post above:

What is HRV?

MVHR = Mechanical Ventilation and Heat Reclamation

If you're not clear and accurate when you refer to something like MVHR the Forum readers may get confused - or I will!

Your post will be of limited use to others, which is what this forum is really about, not just the exchange you're in at the moment.

Thanks. 

ONQ.


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## tred (13 Mar 2010)

*Re: Go air tight but forget about MVHR*

HRV == Heat Recovery Ventilation.  I assumed this is what the OP was discussing. 

Apologies if ones written skills are not up to ones standard. 

I do often find that a short and sweet to the point reply can be as effective as a short story. 

The Direction this post should have taken was to ask the OP how he was going to decide on a ventilation system for his new build over, an attack on his skills as self builder. 

He may not have the choice. Boots, one bit of advice. Get experienced tradesmen with good recommendations and see their work.


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## onq (14 Mar 2010)

*Re: Go air tight but forget about MVHR*

Clear concise posts are always welcome, and thanks for making the effort.
Advising people to be led by experience as opposed to competence - less so.
Experience that may have been gained gained building 9 inch [225mm] hollow concrete block rendered construction is less than best practice when dealing with current highly sealed houses that rely on timber frame technology.
Also be wary of "experts" who have not served their time on any one trade and may only have been "mates" with Third Year Apprentices - the industry abounds with these geniuses who may know all the short cuts but have not achieved all the skills and standards necessary to be a master tradesman.

The OP as self-builder assumes the role of Main Contractor under the Health and Safety Regulations.
This is not a role to be undertaken lightly by someone with next to no skills or experience who may on his first build, who may not ever have built even a shed or an extension for storage and who's now jumping in at the deep end building a habitable dwelling in substantial compliance with health and safety legislation, planning permission and the building regulations.
So on AAM we try to give the best advice we can to everyone who asks, because self-builders constitute 30-40% of new build dwellings annually and they are largely unregulated and not overseen by members of the building professions.

This can sometimes include calling a spade a spade and asking people to post clearly.
Other than that we are pretty tolerant of contributors who commit to high standards.
And we are welcoming of people whose advice may challenge the accepted norms.

So long as they can support what they say.

ONQ.

[broken link removed]

All advice on AAM is remote from the situation and cannot be relied upon as a defence or support - in and of itself - should legal action be taken.
Competent legal and building professionals should be asked to advise in Real Life with rights to inspect and issue reports on the matters at hand.


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## boots (15 Mar 2010)

*Re: Go air tight (eg Q50.3) but forget about MVHR (Mechanical Ventilation Heat Recove*

Hallo Tred,

Thanks for your response and support.

Firstly re the 10k - that comes from the following:


Cost of MVHR unit plus ducting - 5 or 6k approx
Suspended ceilings to both floors to facilitate ducting - whether you use double battens or the metal system you are still doing extra work here. I know one house which had a lot of work done to take the ducts - approx 1 - 2k
Next is the bit that I am really learning as I go - many people will tell you that MVHR is terrific, ask them what level of airtightness the house should have with MVHR and / or the air tightness they have in their new MVHR house - I have yet to hear the right answer, or any answer to be honest. My research is telling me that Q 50(3) or so is what you need with MVHR. To achieve this you need to spend money. I think this will mostly go on plastering the internal face of the blockwork before you put on the plasterboard. A lot of the other sealing around opes and windows etc is also very important but should be done anyway whether or not you are using MVHR, imo. I have been quoted an addtional cost of 12-15k to bring my proposed new build up to a Q50-3 standard. Assume this cost is somewhere in the right ballpark of 10k plus, then I think that a lot of it is worthwhile anyway so I would attribute 5k directly to attaining Q50-3. And maybe 5k to lift you from a poor Q50-10 (building regs) to a more decent Q50-5 or 6. Rough calcsI know but not too wrong either
So now I am at a figure of 10 - 12k, which doen't factor in the maintenance costs after your warranty expires, I'm guessing 400 euro p.a., based on one call out and a few filters etc - this cost will have to be paid forever.
When the unit packs up, as it invariably will albeit some time in the future then you will have to stump up again - another 3 - 4k??
For all these reasons I am thinking of not spending this 12k of borrowed money and using it elsewhere, 
Good luck with your build.

boots


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