Air-tightness ( foam V tape )

a_noodle_jenny

Ok so we are onto plasterer and Windows this week... Engineer and builder were out and we have a number of big decisions to make
My biggest query / concern is the major leaning pushing the architect and engineer and builder are doing towards using expanding foam rather than tape to seal airtight membrane... We are not building a passive house and not heat recovery pump but my parents built a well insulated (for the time) house in 2002 and I am well familiar with the draughty spots so this being our first home after years of planning permission issues I don't want draughts and cold spots in our home.
From what I read before the tape is the only solution... But they are really pushing this and have my hubby convinced that it will cost a huge amount and that its argue amount of work... Ok so obviously it's a lot of work and the tape is expensive but is this not what a mortgage is for??
It is my understanding that the expanding foam is insulation but does not make the building airtight. We are going with 1.2 for Velux roof Windows but I'd say if our budge allows we hope to go for triple glazed Windows with value of <0.8
Please excuse my lack of building lingo and obvious lack of knowledge on Windows but these men are really pushing this and in my experience the easy way for them is often not the best way...

BarneyMc

a_noodle_jenny wrote: »

Ok so we are onto plasterer and Windows this week... Engineer and builder were out and we have a number of big decisions to make
My biggest query / concern is the major leaning pushing the architect and engineer and builder are doing towards using expanding foam rather than tape to seal airtight membrane... We are not building a passive house and not heat recovery pump but my parents built a well insulated (for the time) house in 2002 and I am well familiar with the draughty spots so this being our first home after years of planning permission issues I don't want draughts and cold spots in our home.
From what I read before the tape is the only solution... But they are really pushing this and have my hubby convinced that it will cost a huge amount and that its argue amount of work... Ok so obviously it's a lot of work and the tape is expensive but is this not what a mortgage is for??
It is my understanding that the expanding foam is insulation but does not make the building airtight. We are going with 1.2 for Velux roof Windows but I'd say if our budge allows we hope to go for triple glazed Windows with value of <0.8
Please excuse my lack of building lingo and obvious lack of knowledge on Windows but these men are really pushing this and in my experience the easy way for them is often not the best way...

Not sure this is the thread to use for your query? Anyway, what junction are you talking about? If it's window-wall then tape is the way to go as the ultimate airtight barrier.

Bad_alibi

a_noodle_jenny wrote: »

Ok so we are onto plasterer and Windows this week... Engineer and builder were out and we have a number of big decisions to make
My biggest query / concern is the major leaning pushing the architect and engineer and builder are doing towards using expanding foam rather than tape to seal airtight membrane... We are not building a passive house and not heat recovery pump but my parents built a well insulated (for the time) house in 2002 and I am well familiar with the draughty spots so this being our first home after years of planning permission issues I don't want draughts and cold spots in our home.
From what I read before the tape is the only solution... But they are really pushing this and have my hubby convinced that it will cost a huge amount and that its argue amount of work... Ok so obviously it's a lot of work and the tape is expensive but is this not what a mortgage is for??
It is my understanding that the expanding foam is insulation but does not make the building airtight. We are going with 1.2 for Velux roof Windows but I'd say if our budge allows we hope to go for triple glazed Windows with value of <0.8
Please excuse my lack of building lingo and obvious lack of knowledge on Windows but these men are really pushing this and in my experience the easy way for them is often not the best way...

Your arch, engineer and builder are idiots that's the simple answer. Expanding foam is not Airtight. It will seal the junction but in a few short years it will degrade and if will be like it was never there. A €100 with buy a couple of rolls of pro clima tescon vana profile tape and it'll take your husband a weekend to tape the Windows.

BarneyMc

Bad_alibi wrote: »

Your arch, engineer and builder are idiots that's the simple answer. Expanding foam is not Airtight. It will seal the junction but in a few short years it will degrade and if will be like it was never there. A €100 with buy a couple of rolls of pro clima tescon vana profile tape and it'll take your husband a weekend to tape the Windows.

There is certified airtight expanding foam (one of the main ones you'll pick up in a DIY store and saw it yesterday) but yes, its application is not to be a long term airtight barrier.

BryanF

mod note: Moved from 'live self builds' to own thread

Op
This is a tough one.
Tape is better than foam, being ganged up is not the way you should be convinced..

The tender spec should state the proposed air-tightness level and the contract addendum should have specifically referred to a set air-tightness level as a requirement.

suggestions at this stage:
Convincing your building team means bringing in a couple of specialist air-tightness installers,really just to quote - but also give you the opportunity to ask questions (and meet the builder/eng/ husband) - you obviously need to have Sussed the them out first

Immediately seek an air-tightness course for all 4 of you to go on, they are typically a 1 day with CPD points so not hard to convince a professional builder / eng, as they are typically supposed to do approx 40 cpd hours per year for their professional chartered membership, they are not expensive.

If foam is being suggested, please tell us the inside of the block walls are being plastered? And not just the drylining boards? ( there are several items in your op that could also be questioned, but let's stick to air-tightness)

Ask the builder for the number of home owners, where he has carried out an air-tightness test previously. Ask the eng the same.

Ask to see the engineers 'provisional BER specification' in terms of renewables, air-tightness, & ventilation

Best of luck

Calahonda52

OP: as above plus:
You seem to know a lot about whats going on so hats off!

Can you clarify where exactly they want to use the foam when you write.

using expanding foam rather than tape to seal airtight membrane

Also what is being used in the house as the airtightness membrane?

Will send u a link to some videos from the same stable as the product what bad alibi mentions....

Jut an update on what MT says below, OP if you are in Leitrim, and want to contact someone in Sligo who does this for a living, reply to my PM

Metric Tensor

Properly applied tape is the key in the majority of cases in my opinion. I know at least one manufacturer that makes an air tightness foam and I have no problem with it as a secondary/auxiliary measure.

As above it all depends on the air tightness plan for your house.

As a related aside I have found that people who specialise in air tightness work on houses are generally better value than one might expect and it is definitely the type of work that benefits from regular experience. I have tried to tape windows myself and after spending three times as much time I still ended up with a job that was only half as good as a good "air-tightness man" - and I even knew what I wanted to achieve which is a step up from the man in the street.

sydthebeat

Hang on.... "Air tight tape or foam to seal membrane"...????

The membrane manufacturers will specify exactly what product is suitable to seal it to different substrates. Anything else will void warranty.

MicktheMan

OP, without knowing your air tightness target (and strategy), it is difficult to give proper advice here. However, expanding foam is not airtight when compared to proper taping, period.

a_noodle_jenny

Thanks so much to you all - I'm like a bloody Junior Infant here and I really appreciate all the input. We don't have targets as regards Airtightness. There are a few grey areas as regards the spec from architect/engineer and quote from builder. We are subcontracting also so we are learning as we go...
150mm cavity with beading insulation
150mm insulation sub floor
There are 27 windows and 7 Velux Windows (BDX tape has been recommended for these)
Plasterboard/ theromboard on external walls (I think the thickness has to be decided)
The foam is for the rafters upstairs and the Windows was mentioned also... The argument against my concerns is that it will be costly and time consuming.
I have also asked for the blue seal goop (Fortax Gerband I think - seen on this forum) in the chasing and ducting and services. It's little things like extractor fans only opening when in use etc I feel I have really picked up so much and when I spoke with all the men on site it was like I was taking gobbeldy gook. I find when talking with service providers then they have a sale in mind and so push their own agenda...
This forum is more open and I'm so pleased with others who echo my concerns in spite of my obvious lack of detail and baseline knowledge.

BryanF

OP let me reiterate the need for plastering the inside face of the BLOCKwork, do not believe those who suggest the plasterboard slabs are the AT layer.

MicktheMan

a_noodle_jenny wrote: »

150mm cavity with beading insulation
150mm insulation sub floor
.......
Plasterboard/ theromboard on external walls (I think the thickness has to be decided)

OP, given the above rough spec, you are building a reasonably insulated but draughty house (like a lot of houses being built these days) that will cool down quickly when the heating is turned off. I believe this is not what you want.
Just take the walls for example; where is the air tight barrier? Ask your engineer/arch/builder. No matter what they say, there isn't one, unless the inside of the external blockwork is properly plastered (it is then to this plaster that the windows are taped to), because unplastered blockwork is porous to air. The insulated plasterboard will not address this (as alluded to by ByranF earlier) and is in fact a utter waste of money and space.

a_noodle_jenny

Yes Bryan, the plasterer specified for this plastering layer to be done in the layer between the block work and plasterboard. Mick thanks also for your input... It's most helpful

Bad_alibi

a_noodle_jenny wrote: »

Yes Bryan, the plasterer specified for this plastering layer to be done in the layer between the block work and plasterboard. Mick thanks also for your input... It's most helpful

Far cheaper to go with 200mm wide full fill pumped bead in the cavity. Insulated slabs internally is a shocking bad detail from your arch/engineer. It stinks of laziness.

a_noodle_jenny

Well hopefully if we have made the wrong decision on the cavity size we can gain some of this back through other methods. I believe when cavity size was being discussed the house layout was an issue... If this information was incorrect then so be it, otherwise I'll be driven mad by the end of this build. It's not the house I would have chosen for us but we were very limited in what we could do due to planning difficulties spanning back 6 years

Like anything at the time we can only go on the information we have at the time. OH is going to call an insulation guy tomorrow to discuss our options. He has fully taken on board all the comments in relation to spray foam insulation in rafters and the tape on Windows and elsewhere throughout house.
To be informed is key to getting somewhere and despite the scant information provided from my end We have pieced together some form of a case for keeping well-clear of the foam.

To add to this I grew up in a 1930s concrete block bungalow with high ceilings and an open fireplace in my bedroom... I could see my breath in winter and the walls and windows used to have condensation on them... And the black speckled mould on the wall paper with the thin foam underneath. Current rental is built 10 years and has different problems but again related to insulation (or lack thereof)

Thanks again. I'll update this thread as more decisions are finalized relating to Airtightness

murphaph

The tape isn't that bloody expensive. In our (0.8 ACH @ n50) house there must be rolls and rolls of SICRA tape used (three different kinds of the stuff are in our house depending on application). They did use a special glue however to bond the plastic membrane (it's timber frame ground and first floor) to the ground floor slab. That wasn't taped but I don't think it was supposed to be either.

Good luck and remember that some guys calling themselves professionals are not. Nobody will care more about this build than you.

a_noodle_jenny

So an update on the Airtightness concerns today. We met on site with an independent person who went through our concerns. We are both still Junior Infants when it comes to Airtightness but I would say that we are much more informed.
We now have to decide on the level of insulation we want but it would seem that we will go for membrane and tape. On the roof we need to batten vertically and then horizontally for the slates. We are looking at 9" of insulation between the rafters. There is only space for 7" but this can still happen at the stage of the build we are at now - just about.
I will update as we go...
I would add that this person was not an advocate of the foam and voiced the same concerns that I see here on Construction and Planning threads here on boards.

a_noodle_jenny

A lot has changed in a few days... Due to the level of insulation and taping that is underway we now have to look at ventilation systems such as Air to Water Heat Pump. The MVHR is out of our budget and even if it was within our reach I would be concerned that the settings, rads upstairs could be calibrated incorrectly... I'm seeing a number of ongoing issues arising from these systems on here and we both would lack hugely in knowledge in this area.
We have opted for reclaimed blue Bangor slates and so perhaps if the Heat Pump would replace the solar panels this is the best option of us (Part L)
We are getting a preliminary BER done this week.

I think we might go with those Dimplex Smart Rads anyways regardless of ventilation system. They sound exactly what we need upstairs. Our current timber frame house (rental - built 2006) is so hard to regulate in temperature. Some rads don't turn off at all and house gets too warm at times just to heat our water. Also due to the huge variance in temperature in this country from one day to the next a smart system is the way forward.
We just turn heat off on the wall and then I wake at night cold... Also not good for sleeping babies. This insulation and heating system will change our lives.

893bet

Air to water heat pump is nothing to do with ventilation? A MVHR has nothing to do with calibrating rads (not even sure what this is). Who told you this?

If going air tight a mechanical ventilation system is not really optional. You will be making a huge mistake by only focusing on insulation and heating.

a_noodle_jenny

Sorry folks,

I really should get my information right.
The options we have from our insulation consultant are products such as

Niland Comfort P
or
Aereco mechanical ventilation system

So if I'm making sense we have to use some sort of ventilation in the house now due to the membrane and sealing we will be going with.

Our guy will sit down with us again and go through our options. He's not mentioned anything about rads so disregard that as this was only something I picked up wrong from other threads