Putting a price on u-value?

Wolfhound14

I would like some thoughts on the following dilemma.
I recently sent out my planning drawings to a number of builders and have arrived at the following decision point. (2880sq.ft. Single Story...lots of roof)

Builder A: Traditional Block Build, 100mm Cavity with 60mm insulation and dry lined = $154K (U-Value is 0.24??)
Builder B: Traditional Block Build, 150mm Cavity Pumped cavity = €183K (U-Value 0.2)
Builder A: Timber Frame - Closed panel system with reported uvalue of 0.15 = €190K (i.e. Kit is 68K, builder has quoted 122K to finish)

The reason for the different spec is purely down to my Newbie status. Our engineer's spec was simply not up to standard, but as a result I need to justify spending 30K-35K for this improvement.
Can this be easily justified? Especially as this will ultimately be borrowed money.

The prices quoted are for the structure as I PC Sum'ed Doors/Windows, Heating/Plumbing, Electrics.
So many more dilemma's to come:)

rayjdav

Wolfhound,
My opinion, for what it's worth, on this is that, like all of us, you have to live within your means. If you can afford the top rated house, along with all the money and eco:rolleyes: savings, go for it. If you find that, because of mortgage repayments you will be living to work, as opposed to workng to live, re repayments, I know which one I would go down. Simple hard life fact.

Naturally, you do get what you pay for, that goes without saying.

You are going to get expert advise on here saying the top u-value is the only way to go but, as you say, that price excludes windows/plumbing etc, you have to sit down and see what noose is around your neck for the next 30-40 years.

I have had clients reading about this and that technology and wanting it in their home but when they did their sums, it is quickly forgotten about.

Your life, your money, but just my opinion.

Not I'll get off my box as my rant is over.:D

sydthebeat

Wolfhound14 wrote: »

Builder A: Traditional Block Build, 100mm Cavity with 60mm insulation and dry lined = $154K (U-Value is 0.24??)
Builder B: Traditional Block Build, 150mm Cavity Pumped cavity = €183K (U-Value 0.2)

that doesnt make sense...... 150 pumped cavity should actually be less expensive than 60mm board and internal dry lining.

did you send each spec to each builder???

Wolfhound14

sydthebeat wrote: »

that doesnt make sense...... 150 pumped cavity should actually be less expensive than 60mm board and internal dry lining.

did you send each spec to each builder???

Thanks Syd. I only had one spec done. Builder A quoted for it as spec.
Builder B is a larger company and their standard is now the 150 pumped.
As a larger company I assume they have bigger overheads and that may explain the difference?

I went off and got the TF quotes myself, asked Builder A what was cost differential if we used timber frame. His cost went down 32K but the frame is 68, so thats where I am. ( I'm sure I can get the diff down to 25-30 if I sign up i.e. discounts from both)

There is a Builder C who has TF experience but I am still waiting for a quote from him.

ninjaBob

@Wolfhound14

Just sent you a PM

bravojohnny

Once you go larger than your standard 100mm cavity, it will require a larger foundation & it will have to be designed by a structural engineer, maybe thats whats driving up the price of Builders B's quote?

sydthebeat

bravojohnny wrote: »

Once you go larger than your standard 100mm cavity, it will require a larger foundation & it will have to be designed by a structural engineer, maybe thats whats driving up the price of Builders B's quote?

not necessarily.....

cavities up to 150mm are dealt with in appropriate BS.

Specific structural engineers are definitely required over 150mm

Information Seeker

bravojohnny wrote: »

Once you go larger than your standard 100mm cavity, it will require a larger foundation & it will have to be designed by a structural engineer, maybe thats whats driving up the price of Builders B's quote?

Its when the cavity is larger than 150mm, you need a structural engineer.

bravojohnny

Information Seeker & sydthebeat thanks for the information.

ardara1

sydthebeat wrote: »

that doesnt make sense...... 150 pumped cavity should actually be less expensive than 60mm board and internal dry lining.

did you send each spec to each builder???

Possible additional costs in wider cavity -

Additional excavation & disposal
Additional concrete to foundation
Additional reinforcement to foundation
Additional cavity fill concrete
Radon barrier/DPM increase.

EXTERNAL WALLS
Wall ties – Increase in quantity / dimensions / low conductivity
Increase in cavity closer dimensions
Increase in reveal width.
Increase in cill board dimension
Additional plaster & paint externally

ROOF
Additional costs associated with roof etc
Longer rafters
Closing cavity at wall plate.
Extra tiles/slates

sydthebeat

ardara1 wrote: »

Possible additional costs in wider cavity -

Additional excavation & disposal
Additional concrete to foundation
Additional reinforcement to foundation
Additional cavity fill concrete
Radon barrier/DPM increase.

EXTERNAL WALLS
Wall ties – Increase in quantity / dimensions / low conductivity
Increase in cavity closer dimensions
Increase in reveal width.
Increase in cill board dimension
Additional plaster & paint externally

ROOF
Additional costs associated with roof etc
Longer rafters
Closing cavity at wall plate.
Extra tiles/slates

and id still argue cheaper than internal dryling the external envelope.....

MicktheMan

Wolfhound14, it is possible to approximately work out which is the better option (assuming the stated u values are actually achieved!). What you should end up with is what the extra mortgage is going to cost minus what will be the savings on energy consumption. Basically you can work out the heat loss through the walls for the different options and then assume an inflation rate of energy over the period interested in, say 30 years, and work out what the benefit is in today's money taking into account the extra payments on the mortgage. Sounds complicated I know but it can be done.

BUT
It is also important to remember that your walls are only one area of heat loss in a house. The u value of the windows/doors, frames and their installation, floor, roof and not to forget airtightness are also extremely important if a low energy house is required. Also, if significant thermal bridging is designed into the house this can have a detrimental effect on the heat retention properties of the house.

Imo, you cannot just look at the wall spec in isolation.

Information Seeker

MicktheMan wrote: »

Wolfhound14, it is possible to approximately work out which is the better option (assuming the stated u values are actually achieved!). What you should end up with is what the extra mortgage is going to cost minus what will be the savings on energy consumption. Basically you can work out the heat loss through the walls for the different options and then assume an inflation rate of energy over the period interested in, say 30 years, and work out what the benefit is in today's money taking into account the extra payments on the mortgage. Sounds complicated I know but it can be done.

BUT
It is also important to remember that your walls are only one area of heat loss in a house. The u value of the windows/doors, frames and their installation, floor, roof and not to forget airtightness are also extremely important if a low energy house is required. Also, if significant thermal bridging is designed into the house this can have a detrimental effect on the heat retention properties of the house.

Imo, you cannot just look at the wall spec in isolation.

good point, well said.

Wolfhound14

Thanks Mick.
I am certainly not only looking at walls, but I reckon this single payment will be over 50% of the total cost of my finished construction.
I am actually leaning towards the lower spec walls and using that 30K to improve the efficiency of the other components that you mentioned.

sinnerboy

Wolfhound14 wrote: »

(2880sq.ft. Single Story...lots of roof)

Having done a few DEAP calcs on similar builds I believe you will need to get down to a wall U Value of 0.2 min to simply comply with B regs .

( and 0.16 roof and 0.15 floor and 1.4 whole window and 6m2 solar and wood stove - no open fire - and Q50/5 AT)

This is an educated guess - I advise you appoint a BER assessor now to run the calcs for you .

.

Wolfhound14

Thanks Sinnerboy.
The engineer did a prelim DEAP and it met regs, but I think the main factor was triple glazed windows at u = 0.9. (My target is definitely not to just meet regs)

Met with a third builder last night and his price was about 50K more for the traditional block build with another 10K for TF, so looks like Builder A is the man.
(I know the house is not as simple as it might be, but over €100/sqft for builders finish is surely excessive)

After much soul searching and assuming I can get the differential price down to 25K, I think we will be going with the TF for c. €180K.
I was originally looking at geo thermal etc but now I think the 25K is better spend on walls.

Full plan now is:
Timber Frame, Solar Panels, Condensing Oil Boiler, UFH, Airtightness to 2 ach/hr and HRV.
We have 2 chimneys, so looking at 2 Stoves. (Probably one wood, one multi fuel)
I will probably look at putting a back boiler on one with the intent of plumbing it into a thermal store that is connected to the UFH and boiler.

Wish me luck...and thanks for all the input.