insulation

kenthehen

hello in the process of the insulation stage for a new dormer bungalow , I have got the foam spray done between the rafters and am now deciding the best way to insulate the knee walls and ceiling joists , im thinking of 100 mil cosy board in knee walls and ceiling joist , then wrapping the knee walls and ceiling with airtight membrane, does anyone have experience or advise in this , muchly appreciated thanks .ive heard that cosy board is better than fibreglass ???

Calahonda52

whats your approved certifier/engineer/architect/etc saying or are you just winging it here.
It could be argued that you don't need to do the knee wall. ceiling if the foam spec is up to the required standard to allow the space be used as conditioned storage

kenthehen

kind of just winging it here to be honest , architect has insulated boards for knee walls and ceiling etc and has said to use fibre glass in attic, I got icyene spray in foam so its good spec I hope !!!, going to use some of the knee walls for storage,its hard to know the right way to insulate a dormer bungalow, id be afraid I would over insulate and it be to hot in the summer !!!!plan on using the airtight membrane as well , architect didn't call for that .

sydthebeat

you should have just sprayed from eaves to ridge

kenthehen

sydthebeat wrote: »

you should have just sprayed from eaves to ridge

I did spray from eaves all the way to ridge ??

sydthebeat

kenthehen wrote: »

I did spray from eaves all the way to ridge ??

so why do you need to insulate the knee walls and ceiling joists???

kenthehen

sydthebeat wrote: »

so why do you need to insulate the knee walls and ceiling joists???

I taught you have to insulate knee walls and ceiling above. Lot of people have complained about knee walls not been insulated . Do you think i have no need to do it . That be great if i dont

BryanF

Where is the air-tightness envelope planned? Eaves or knee high walls? What measures were taken before joist were installed?

sydthebeat

kenthehen wrote: »

I taught you have to insulate knee walls and ceiling above. Lot of people have complained about knee walls not been insulated . Do you think i have no need to do it . That be great if i dont

you need to insulate your building envelope to relevant standards.

so either ensure the sloped rafters are insulated adequately, which means you dont have to insulate the knee walls and joists...

or, if it isnt insulated adequately, you then need to insulate the knee walls and joists.

the former is a better job than the latter.

did you not have a preliminary DEAP assessment carried out prior to commencement??
how does your certifier know whats being built complies with building regulations?

kenthehen

Didn't joist . Precast floors i used . Have to pour screed on top of that. So was planning doing the airtight membrane from the knee wall up and across ceiling down to floor.

kenthehen

Architect done drawings etc . I've no need for an.engineer etc . I got planning permission before the new law came in regarding engineers signing of in everything bit of a money racket that . Sure who is going to build there own house wrong

sydthebeat

kenthehen wrote: »

Architect done drawings etc . I've no need for an.engineer etc . I got planning permission before the new law came in regarding engineers signing of in everything bit of a money racket that . Sure who is going to build there own house wrong

ehhh YOU?

Calahonda52

who will sign off that the work has been done in accordance with both planning and building regs or will you just wing this as well, Icarus-esqe-like perhaps.
https://en.wikipedia.org/wiki/Icarus

Strolling Bones

kenthehen wrote: »

Sure who is going to build there own house wrong

kenthehen

Ha ha ah not a chance ill build it wrong. Everything is structurally sound . Even put on wall plate straps and on the gables because surely if the roof decides to move the straps will hold it together !!!!!! (sarcasim there own)Ah know thanks for all your advice lads appreciate it .

BryanF

Air-tightness seems to be already irreversibly comparmised.

kenthehen

Ah won't try airtightNess want to have fresh air in the house

BryanF

I leave it there so

Strolling Bones

kenthehen wrote: »

Ah won't try airtightNess want to have fresh air in the house

MicktheMan

kenthehen wrote: »

Ah won't try airtightNess want to have fresh air in the house

This gets better and better. Thanks for the laugh.:)

delfagio

Kenthehen,

I am no expert builder, I'm an engineer and am building our new build house with my wife also, but maybe you should stop now, step back, do some research on energy efficiency as well as the current building regs and get an engineer or architect on board to see what you can do now before you go any further......forgive me but this sounds like it could be the house that Jack built.

The idea of airtightness isn't a made up thing. It's main purpose is to make the house more energy efficient.....basically your saying you won't bother with the whole airtightness thing and that you would like your house fresh.....let me put it this way to you.

Say your house gets an airtightness level of say 10m3/hr......which doesn't meet anywhere near current building regs, and say my house or somebody else's new house gets a level of 1m3/hr....this basically means you will have to heat YOUR house 10times every hour while say I or someone else would have to heat the house 1time every hour....so in MONEY terms, if my house cost 300euro on oil to heat a year yours could cost roughly 3000euro......this is just very simplistic terms, I'm not getting very technical on it as I would be no expert......but I hope you can see the big reason for airtightness here.

I'm going to guess that your haven't done any airtightness tapes around your Windows and doors or any cables, waste pipes etc passing through the external walls. Or did you???. If it's not to late to do so......I would make sure you get a competent person to do this for you. It may seem like more money to do this now but it will save you in the future long term.

Just listen to the likes of Mick the Man, strolling bones and Bryan F and others...these guys know their stuff. I have read many posts they have put up on Boards to help and guide people.

You can insulate the hell out of the house.....put 600mm on walls roof floor etc if you want...just exaggerating here, but if your house isn't airtight, as soon as you turn your heating off the house WILL cool down, and fairly fast I would imagine, and then you will have to put the heat back on.

Seriously, just stop and get a professional person in now to help you going forward if it's not too late.

Also you Must have an engineer on board / assigned Certifier in order to build your house to say it is built to regulations and standards. You need these alone just for mortgage drawdowns from the bank.

Oh and you also mentioned that your architect didn't call up for airtightness to be carried out.......get rid of him now.

Hope you take this on board for your sake or you WILL build your house wrong.

kenthehen

Thank you for your message i apologise if i come across that i don't care about airtightness . Yes i have taped windows. I am sand and cementing external walls . Then insulating board . I have rafters sprayed with icynene spray.the best on the market. Knee walls with 100 mil cosy board .any gaps etc sprayed with can of insulation foam. . .Ceilings knee walls installed with insulated board.

GOGRAHAM

sorry for diverting from the original questions on thread, but just read it all and i have a question regarding air-tightness, (im no builder or structural engineer so i could be way off the mark here)
So you are basically saying tape up everything and foam all gaps etc. but then you have to go and put a vent in each room anyway? does this not null all the work you put in trying to make it airtight?
as i thought if you had no vents you would end up with a damp moldy room?
Just based on my limited experience with new house (built in 1970s) that is FAR from air tight (has under suspended floor vents and gaps around cables pipes etc) but i need to add vents to windows to stop damp/mould on them.

MicktheMan

GOGRAHAM wrote: »

sorry for diverting from the original questions on thread, but just read it all and i have a question regarding air-tightness, (im no builder or structural engineer so i could be way off the mark here)
So you are basically saying tape up everything and foam all gaps etc. but then you have to go and put a vent in each room anyway? does this not null all the work you put in trying to make it airtight?
as i thought if you had no vents you would end up with a damp moldy room?
Just based on my limited experience with new house (built in 1970s) that is FAR from air tight (has under suspended floor vents and gaps around cables pipes etc) but i need to add vents to windows to stop damp/mould on them.

Airtightening a house is to reduce convection heat loss from the house (the predominant heat loss mechanism in this country).
Ventilation is to remove moisture & odors from the house in a controlled and intelligent manner. There are far better ways of venting a house than the typical wall / window vents.

Do you drive a car?
Did you ever wonder why car manufacturers go to a lot of trouble sealing the cabin and then go and put air vents in the dash?

GOGRAHAM

MicktheMan wrote: »

Airtightening a house is to reduce convection heat loss from the house (the predominant heat loss mechanism in this country).
Ventilation is to remove moisture & odors from the house in a controlled and intelligent manner. There are far better ways of venting a house than the typical wall / window vents.

Do you drive a car?
Did you ever wonder why car manufacturers go to a lot of trouble sealing the cabin and then go and put air vents in the dash?

I understand why you would airtight a house, to reduce the convection heat losses. but my argument is that in general you are sealing it up then adding vents back in and typically the vents are a hole in window/wall (not much thought in that?)
Am i correct saying modern regulations say there needs to be a 4 inch vent in each room?

regarding cars they seal them for water-tightness and to a lesser extent sound insulation not really heat insulation and its a totally different application. in modern well sealed cars i would imagine you wouldn't last too long in a car full of oxygen sucking passengers if the cabin had absolutely no vents/windows haha

What other ways are there to vent houses other than vents bar expensive air recirc systems?

MicktheMan

GOGRAHAM wrote: »

I understand why you would airtight a house, to reduce the convection heat losses. but my argument is that in general you are sealing it up then adding vents back in and typically the vents are a hole in window/wall (not much thought in that?)
Am i correct saying modern regulations say there needs to be a 4 inch vent in each room?

regarding cars they seal them for water-tightness and to a lesser extent sound insulation not really heat insulation and its a totally different application. in modern well sealed cars i would imagine you wouldn't last too long in a car full of oxygen sucking passengers if the cabin had absolutely no vents/windows haha

What other ways are there to vent houses other than vents bar expensive air recirc systems?

You seal up to prevent convection heat loss / draughts. If this is not done, then internal air which costs money to heat is lost uncontrollably to the outside.
You provide controlled ventilation to allow internally generated moisture out. Simples.
Current building regs require appropriate ventilation depending on level of airtightness achieved.
There are several methods available to achieve this. "Hole in the wall" vents are acceptable (minimally), but, imo, are not a solution for several reasons. A continuous mechanical ventilation solution is better (mev, dcv, mvhr).
I am not familiar with "air recirc systems".

sky6

GOGRAHAM wrote: »

sorry for diverting from the original questions on thread, but just read it all and i have a question regarding air-tightness, (im no builder or structural engineer so i could be way off the mark here)
So you are basically saying tape up everything and foam all gaps etc. but then you have to go and put a vent in each room anyway? does this not null all the work you put in trying to make it airtight?
as i thought if you had no vents you would end up with a damp moldy room?
Just based on my limited experience with new house (built in 1970s) that is FAR from air tight (has under suspended floor vents and gaps around cables pipes etc) but i need to add vents to windows to stop damp/mould on them.

Again I'm no expert in this area, But I think Gograham your mixing up to different types of Building methods. Even though your house ia 70s build it's now very old technology. The advancements in the last 10 years are massive.
in the old days up to 90s the standard way to Vent a room was to put in Wall Vents.
Now the new methods are for an air tight House and Mechanical Ventilation
through an Air Handling unit. It takes air from the outside and mixes it with the air from the rooms passing it through filters and pushing it back into the rooms.
The constant recirculation is what keeps the air in the Rooms fresh while retaining the heat.

JimmyMW

sky6 wrote: »

Again I'm no expert in this area, But I think Gograham your mixing up to different types of Building methods. Even though your house ia 70s build it's now very old technology. The advancements in the last 10 years are massive.
in the old days up to 90s the standard way to Vent a room was to put in Wall Vents.
Now the new methods are for an air tight House and Mechanical Ventilation
through an Air Handling unit. It takes air from the outside and mixes it with the air from the rooms passing it through filters and pushing it back into the rooms.
The constant recirculation is what keeps the air in the Rooms fresh while retaining the heat.

I wish this were true, however unfortunately people often underestimate the importance of airtightness & MHRV. People often get as far as the airtightness but when the budgets get squeezed the MHRV often gets the boot in favor of a more expensive kitchen or roof-light etc.

Despite all the research and products out there people often tend to listen to the "guy" down the road who did "the airtightness" and "you could hardly draw your breath in the house" however they neglect to mention that the "guy" never put in MHRV in lieu of some other item as I have alluded to above and ended up blocking the vents in the wall as the heat was pouring out. Etc etc