Airtightness for new house

liamolaighin

Anyone know if all the new airtight membranes and tapes for walls and roof are worth the money. How much would you be lookin at for 3200 sq/ft house to tape all window and door openings & make roof airtight???

Is this something all BER advisors are now recommending? I want to build a warm house, well insulated, but at same time keep my open fire. Not going passive so is output on membranes worth it or better spent on insulation. Thinking of pumping cavities...

gman2k

I would at the very least tape up the edges of window and door frames, to reduce uncontrolled ventilation/ heat losses.

IMO this is worth it.

sydthebeat

liamolaighin wrote: »

Anyone know if all the new airtight membranes and tapes for walls and roof are worth the money. How much would you be lookin at for 3200 sq/ft house to tape all window and door openings & make roof airtight???

Is this something all BER advisors are now recommending? I want to build a warm house, well insulated, but at same time keep my open fire. Not going passive so is output on membranes worth it or better spent on insulation. Thinking of pumping cavities...

the price depends on your build type.... block build wouldnt have as much need for tapes and membranes as a TF house would typically...

im surprised that you would assume a BER advisor should be your first port of call. Your architect or architectural technician is the construction professional and should be advising you on these matters. The BER assessor may or may not be from a construction background so may not understand the implications of such specifications. If you are serious you should talk to your architect / technician about designing an air tightness scheme. The acceptable / accredited details are a good place to start but may not cover all the specific details that you require.

RKQ

I agree with Syd.
Airtightness is a requirement in the approved details. It will become an important part of future Building Control.

IMO it is important and will save you money. Its an easy way to help future proof your build. Check out manufacturers web site for photographs of installation details etc.

Simple logical steps will make a great difference - especially around the ends of floor joists in blockwork houses.

Infra red cameras and blow door tests clearly show that airtightness works. I put it in my house 6 years ago!:)

mr_edge_to_you

similiar query here - our builder has quoted us €1500 for "air-tightening" our house with a membrane sealer tape. he used more fancy terminology. He reckoned that the tape and materials would cost about €800 and that there would be about 2 or 3 days work for 2 lads.

can i get peoples advice as to whether they think that it is money well spent? i'm not trying to build a passive house - from the start we've adopted a smart/sensible approach. A conscious decision not to lose to the run with insulation etc.

any feedback would be much appreciated. we need to let him know before the plasterer arrives next week.

thanks,

edge.

sinnerboy

mr_edge_to_you wrote: »

similiar query here - our builder has quoted us €1500 for "air-tightening" our house with a membrane sealer tape. he used more fancy terminology. He reckoned that the tape and materials would cost about €800 and that there would be about 2 or 3 days work for 2 lads.

Rough rule of thumb .
1/3 Energy - you will lose through walls / floors/roofs / windows etc
1/3 Energy - you will lose / consume on hot water . More if you have teenagers . Less if you don't
1/3 Energy - you will lose through ventilation - intended and unintended

It is worth investing in reducing this final part
Is the cost reasonable - €12/m2 install price I would suggest as a budget .

mr_edge_to_you wrote: »

i'm not trying to build a passive house - from the start we've adopted a smart/sensible approach. A conscious decision not to lose to the run with insulation etc.

I've watched over 25 years most clients and builders remark " the amount of insulation here is crazy" . And throughout that period progressively the min amount of insulation required by law his risen and risen over that period .

It is set to rise further soon . 2010 regs will see for example a MIN u value for external wall of 0.21 ( currently 0.27 ) i.e. approx 25% tougher to achieve . But , but , but .... it does not end there . The maximum permissible calculated energy and CO2 emission rates will be set at such a level that U Values of 0.15 and even 0.12 may be required

Or to put it in very simple terms - in 2010 - Passive House will become THE BASE LEVEL . I don't agree that you have " adopted a smart/sensible approach" . You are building the Automobile equivalent of what will soon be regarded as a Trabant - very out of date .

.

mr_edge_to_you

Thanks sinnerboy! When i refer to smart and sensible i mean that we are trying very hard to keep our project on budget, doing okay - touch wood. Obviously there's no limit if you have the money! My biggest fear is running out of money, i'm very much a pessimist. Won't be happy until the last cheque is released. I'm an accountant so I need to know is that there is value in the 1500e.

sinnerboy

I understand .

There is an odd perversity in raising building standards ( or any standards for that matter ) during an economic decline . The fact is one is now building a soon to be outdated house . But there is a time value to money i.e if you HAVE the money now to invest in the future - you do so and if you don't , you cant .

Sadly an unwelcome side affect of raising standards will be that fewer houses will be built

I'm walking into grandmother/eggs territory now aren't I - you being an accountant

All I would say is this . UK market research ( sorry I lost the link to it ) indicates that bathrooms and kitchens have a 15 year lifespan . If you are not committed to those orders yet - try to imagine all that bright shiny kit in a skip one day . You may then adjust you spending plans . If the other half lets you

restaurants

gman2k wrote: »

I would at the very least tape up the edges of window and door frames, to reduce uncontrolled ventilation/ heat losses.

IMO this is worth it.

Good idea. This is easy to do and well worth the effort.

holdfast

A conscious decision not to lose to the run with insulation etc.

Let go and break free from the accountant in you, this is one place you are going to get a payback you will have learnt that in college "payback period". just get a 42 inch lcd rather than 46 inch and half you heating and some of electricity bill aswell with a bit more insulation etc. Again make sure the guys doing the work have received training and tell them and get a air tightness test done it required by law and it will make them build the house right.

mr_edge_to_you

Cheers guys, appreciate the feedback. I was close enough myself before hand but I'm trying to convince my OH that it is a few quid we won't regret.

ninjaBob

I would like to point out that you should be focusing on your bottom line. Putting in more insulation now, controlling your ventillation now and creating a good degree of airtightness now will save you money from day 1.

Don't aim for some rating or stamp of approval from Energy assesors, builders, engineers or architects. Simply aim to do everything within your power to ensure once you move into your house that you are saving money. Do it once and do it right.

Also be careful about Energy Assesors and others who give you information they may be mis-informed or simply talking out of their ass. As pointed out a good few of them simply don't have the background to comment.... like myself so I'll stop talking now.

sinnerboy

ninjaBob wrote: »

Don't aim for some rating or stamp of approval from Energy assesors, builders, engineers or architects. Simply aim to do everything within your power to ensure once you move into your house that you are saving money. Do it once and do it right.

Also be careful about Energy Assesors and others who give you information they may be mis-informed or simply talking out of their ass. As pointed out a good few of them simply don't have the background to comment.... like myself so I'll stop talking now.

Apart from ranting and possibly making your self feel better - what is actually useful here ninjaBob ? Think before you post - are you making a contribution ? (Rhetorical questions. )

holdfast

Don't aim for some rating or stamp of approval from Energy assesors, builders, engineers or architects

Ninjabob you seem happy enough to get help from energy assesors, engineers and architects judging from your passed post. maybe cause its free :rolleyes:

ninjaBob

I was making two very simple points:

Investing the money now when it's cheaper, will save you money in the long run.

Not everyone has the background or experience in constructing houses, so don't simply construct the house to get a rating or meet the building regulations. Spend what you can to make a better house and save yourself money in the long run.

Personally I thought they were valid points.

muffler

ninjaBob wrote: »

I was making two very simple points:

Investing the money now when it's cheaper, will save you money in the long run.

Not everyone has the background or experience in constructing houses, so don't simply construct the house to get a rating or meet the building regulations. Spend what you can to make a better house and save yourself money in the long run.

Personally I thought they were valid points.

Reasonable enough points to me.

sydthebeat

ninjaBob wrote: »

, so don't simply construct the house to get a rating or meet the building regulations.

Your points may be valid, if mis-concepted.

Building regulations compliance is a MINIMUM standard, not something to aim for and fall short due to budget!!

'getting a rating' is something that is also legally required, it is not a luxury, its a necessity.

Embarking out on a huge task such as building ones own home is a monumental task. It still exaspirates me how some people treat it with nonchalance.

Having a goal or aim for this task is one of the primary factors in determining whether it will be a successful task or not. In these days of 'cutting cloth to measure' having a goal of projected running costs of the dwelling should not just be A factor, but in my opinion, THE most important factor in building. Whos to say what financial situation any of us will be in in 10 years time..... who would want a dwelling that costs 3-4 K a year to heat in these circumstances.

ninjaBob

Sorry I should have clarified my points a little more clearly:

One shouldn't aim to just meet the building regulations and leave it there, if their budget allows they should try and spend their money where they will achieve the greatest savings to their overall running costs.

While a BER is legally required an A3 house on paper, may not perform like an A3 house.

This is where the experience and knowledge of your engineers, architects etc will come into place.

I used this document (which has been posted here a few times):

http://www.planningportal.gov.uk/uploads/br/accredconbk.pdf

It helped me pinpoint potential problem areas and keep and eye to ensure they were completed correctly.

I personally didn't go with the AirTight Membranes (Block house with 135mm pumped cavity), but did seal around all windows, doors and services with tapes etc.. Given that I used Cozy boards on my external walls, I also ensured that my around my sockets were sealed to prevent any airflow behind the boards.

sydthebeat

ninjaBob wrote: »

One shouldn't aim to just meet the building regulations and leave it there, if their budget allows they should try and spend their money where they will achieve the greatest savings to their overall running costs.

While a BER is legally required an A3 house on paper, may not perform like an A3 house.
.

sorry.,.. i misunderstood.

i agree with these points completely

muffler

Lay of the Smirnoff syd

sydthebeat

muffler wrote: »

Lay of the Smirnoff syd

I'm more of a rum man myself!!

sinnerboy

ninjaBob wrote: »

This is where the experience and knowledge of your engineers, architects etc will come into place. .

Is an entirely different sentiment to

ninjaBob wrote: »

Don't aim for some rating or stamp of approval from Energy assesors, builders, engineers or architects.

and

ninjaBob wrote: »

be careful about Energy Assesors and others who give you information they may be mis-informed or simply talking out of their ass

Your initial post can be interpreted as advice to trust no one but yourself .

Terrible advice . For most people the self built house is the biggest investment they will make . Good advice pays for itself many times over .

You subsequent posts eventually indicate you believe this too .
The matter may rest there as far as I am concerned .

Make mine a Jemmy . Hic !

.

holdfast

I was wrong on jumping the gun on nijabob advice. Just a case of misunderstanding. I return to my stone to eat humble pie

ninjaBob

Not all advice is good advice and bad advice can certainly cause alot of problems with your build.

It's best to be objective about what advice you take onboard, but at the end of the day you are hiring professionals to do a job and that should also be factored in.

sydthebeat

ninjaBob wrote: »

Not all advice is good advice and bad advice can certainly cause alot of problems with your build.

It's best to be objective about what advice you take onboard, but at the end of the day you are hiring professionals to do a job and that should also be factored in.

if you do not trust the person giving the advice... DO NOT TAKE IT.

Im not sure where you are going with all this. If you have had bad advise then fair enough, one bitten etc etc..... but your last few posts seem to throw architects engineers and energy assessors into a basket of professionals not to be listened to. That in itself is very bad advise.

There are good and bad practitioners in all walks of life... its a good client who can seek out the good ones. The basis you use to seek out these good ones would be a factor in how successful you will be.

Naux

ninjaBob wrote: »

http://www.planningportal.gov.uk/uploads/br/accredconbk.pdf

It helped me pinpoint potential problem areas and keep and eye to ensure they were completed correctly.

I personally didn't go with the AirTight Membranes (Block house with 135mm pumped cavity), but did seal around all windows, doors and services with tapes etc.. Given that I used Cozy boards on my external walls, I also ensured that my around my sockets were sealed to prevent any airflow behind the boards.

I have to agree with the sentiment here. I will be taking a similar view when building my house.

The whole airtightness/hrv issue for me revolves around "the law of diminishing returns" The extra capital cost of getting the house virtually airtight to me is not likely to be worth it. Obviously some people want to bring the airtightness etc to the highest standards and fair play to them I say. I would also say however that this approach is not for everyone.


I live in a semi-detached house at the moment(built 2002, basic insulation etc) and I find the house warm. I wonder how I'll cope with living in my new house next year!!

sinnerboy

Do you know what level of air tightness you need to achieve to comply with building regulations ?

What is your advisor telling you - on the back of a DEAP calculation ?

Air tightness is a part-component making up total energy losses as I posted earlier ( post 6 ) . So you can't assess air tightness in isolation .

mr_edge_to_you

decision made. we're going to go with the air tightness. spoken to a few engineers i know and along with all your advice we've decided to go the air tightness membrane.

thanks to you all for your advice! as always, much appreciated.

holdfast

Naux it’s not as simple as that, the saving made up having the right airtightness can bring big savings. The difference between passing and getting a best practice result on the test can save you 30 %. Moreover when you are sitting down in front of the telly with herself and she says I feel a draft around my ankles and the fire is roasting:eek:. Or if you go the other way and the house is too air tight for the planned ventilation you end up with mould, condensation and sick build syndrome

This can even happen no matter how well the house is insulated. Houses are built and ever trade will punch holes in the construction. Any house can be warm when you have put enough heat in it. The test of new house is how little heat or no heat is required. You will also need to have an airtightenss to know if the house has been build to standard. It’s a great way of ensuring the house is build well, think of it as stamp of approval on the work and the money you invested in the house.

No6

I kind of missed this post but having read through it (quickly) no one seems to have picked up the op's decision to have an open fire. As far as I am concerend airtight houses do not work with open fires, he should at least consider a solid fuel room stove. There is little or no point in spending thousands on airtight membranes and then having a big hole in the sitting room!!

Naux

No6 wrote: »

I kind of missed this post but having read through it (quickly) no one seems to have picked up the op's decision to have an open fire. As far as I am concerend airtight houses do not work with open fires, he should at least consider a solid fuel room stove. There is little or no point in spending thousands on airtight membranes and then having a big hole in the sitting room!!

Agreed. I missed the open fire line myself.

liamolaighin

Have actually been considering the solid fuel stove alright since. Think it'd be nice n cozy n improves the BER no end. So if I do go this route would people generally agree that the membranes are a good idea as long as I have enough natural ventilation. Thats the gist i'm gettin so far

sinnerboy

Guess what I voted ?

Naux

Assuming that you put in the airtight membrane and achieve a high level of airtightness in your house, does this mean that you must then install a HRV unit to ventilate the house?

sinnerboy

Yes . If you achieve Q50 / 7 or better then you will need HRV

liamolaighin

So should I be looking at more insulation, using tapes and membranes etc instead of going down the geothermal route. I know the answer is yes I should make it as cheap as possible to heat the house but would it make sence going with geothermal in a house with low heating requirement. I dont want to go with ICF so is there any danger a standard block build with lots of insulation and airtightness will be too airtight. Dont want to spend a fortune either just for the sake of a rating.........

Naux

sinnerboy wrote: »

Yes . If you achieve Q50 / 7 or better then you will need HRV

What would be a rough cost estimate per sqft for the airtightness detail?Is it the 12 euro per sqft as previously mentioned?

From what I've seen in previous posts 5-6k would be the average cost of a HRV system. Open to correction of course!

I'm just trying to get an idea of the total cost or making a house airtight. I know you will definitely save on energy costs with it but I'm just wondering about the capital costs/outlay to achieve it.

sinnerboy

Those are ok budget costs . It is difficult to know what to do - if you don't do a DEAP assessment .

With a DEAP assessment to "play" with you can look at alternative methods of complying with b regs and do cost/benefit exercises then .

Your shooting in the dark otherwise

Lightning McQue

Folks

I did a deap assessment which indicated that I would be making the house airtight and putting in a MVHR system but the MVHR had a negative impact on the BER whereas the triple glazing had a positive impact on the BER.

It seems that holes in the walls (natural ventilation) were better from a BER perspective than a controlled ventilation system. It seems strange.

Anybody else had this type of experience?

lightning

sydthebeat

Lightning McQue wrote: »

I did a deap assessment which indicated that I would be making the house airtight and putting in a MVHR system but the MVHR had a negative impact on the BER whereas the triple glazing had a positive impact on the BER.

a few points.

1. DO NOT use the default HRV values,, they are terrible. Search the SAP Aeppndix Q for figures, choose a decent efficiency and fan power.

2. HRV systems show energy conservation at good levels of air tightness. 0.5 air changes per hour is not good.... aim for at least 0.3

3. building shape has a significant effect on HRV systems. Large single storey buildings with angular forms will fair worst. Compact two storey etc fair best.

holdfast

Hi lighting go to the sei website and download the correct procedure for dealing with HRV. Use the default if you cant find the unit on the sap index. You have been using the default unit setting which are very poor when comapred to units on sap index.

Ferocious

Syd, just picking up point 3 there.
I'm building a single storey house. Like some of the previous posters, I've been deliberating about airtighness membranes & HRV systems. I intend to tape up windows, doors and wall/ceiling junctions, just not sure if this is enough.

How much less efficient is HRV in a single storey?
I haven't done the DEAP calculation yet, will this make it clear if there is much to be gained by using mhrv?
At what stage of construction should the first air-blower test be done?

holdfast

The first test should be done after windows are in and the house is sealed. Yes it will make it clear to you to put in air tightness test results and hrv unit details into deap to show how much energy could save. the loss in % eff will depend on how complex the deign is more turns in pipes more the loss which is the same for complex strucutres to lose more energy due to greater surface area.

Lightning McQue

Folks

I used the SAP appendix, 90% efficiency and 0.3 air changes. The house is a two storey with an angular shape. I presume this explains it or is it the electricity the fan will use?

Lightning

sydthebeat

Lightning McQue wrote: »

Folks

I used the SAP appendix, 90% efficiency and 0.3 air changes. The house is a two storey with an angular shape. I presume this explains it or is it the electricity the fan will use?

Lightning

whats the specific fan power?

have you any chimneys or open flues?? any intermittant fans included?

what sq ft?

Lightning McQue

Syd

I cant remember the specific fan power.

I just remember the assessor inputting the xpelair unit and it had a 70% efficiency which is poor and he then increased this to 90% to see what effect this would have. So I will look for another company. The assessor said that the HRV was costing me money and that I shouldnt put it in, that I would be better to go with natural ventilation. Confused at this stage or is the software flawed.

I will be installing two fireplace inserts.

The area of the house is 314m2 and if I convert the attic it will add another 40m2. I am making provision for this.

Lightning

gizmo555

Lightning McQue wrote: »

The assessor said that the HRV was costing me money and that I shouldnt put it in, that I would be better to go with natural ventilation. Confused at this stage or is the software flawed.

Very interesting and detailed discussion on Mark Brinkley's blog "House 2.0" here:

http://markbrinkley.blogspot.com/2009/11/whither-mvhr.html

I suppose the key point to bear in mind when considering your assessor's comment is that HRV is not just about saving energy and reducing costs.

morning delight

On the question of airtightness, I've chatted with the architect and an energy consultant and the feeling is 1.5m3/hr is what we can hope for with best practice blockwork cavity wall construction.

My question is, Is trying to get this down to 1m3/hr worth it?

mr_edge_to_you

Well it's all in now anyway. Seeing it in makes easier to see how it will be valuable in the long term. Thanks again guys.

Technophobe

Hi Mr Edge to you...

Can you maybe describe in a little detail what exactly they did for you and using what..??

This may help all interested here to understand more clearly what the concept involves (in your case anyway)and what you/they get for their money to a degree (you have previously stated your costs per your builder in an earlier post)...

thanks

mr_edge_to_you

Technophobe wrote: »

Hi Mr Edge to you...

Can you maybe describe in a little detail what exactly they did for you and using what..??

This may help all interested here to understand more clearly what the concept involves (in your case anyway)and what you/they get for their money to a degree (you have previously stated your costs per your builder in an earlier post)...

thanks

In my plain language here goes:

First off all, all window and doors were taped around with "Airstop" tape. It's about 1.5inches wide and looks like cheap paper tape but it is actually quite strong.

There is also a few rolls of a heavy duty plastic membrane running under the ceiling (1st floor/attic) joists and down about 2 metres on the wall plate. All the these various sheets are overlapping and sealed over with the aforementioned "Airstop" tape. The plasterboard is then put on over the membrane. He has only used the membrane between the frist floor ceiling and our attic.

Looking at the work involved it is all labour! Builder said as much himself. He has said he has kept the cost to a minimum so it should be a few hundred quid less than €1500. You could probably do it all over the house from top to bottom (applying the membrane sheeting) but it would cost an awful lot by the looks of it -I'm open to correction on that though.

That's about as much as I know about it. Sorry.