building on a budget

keru

Hi all. I am looking for advice to work out the best way to go about our build. I dreamt of a lovely TF passive house with natural insulation, but the budget wont allow it. So time to compromise but hopefully cleverly!
I'd welcome anyone's realistic suggestions as to how to insulate a TF to reach Part L guidelines for u-values in an economical way but using products that have good health/environment credential?
Thanks!

toastedpickles

These guys were my former lecturers, they're pretty good at what they do and they can pull some amazing things out of the bag
<SNIP> you might get your dream house after all

Best of luck


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BryanF

toastedpickles wrote: »

These guys were my former lecturers, they're pretty good at what they do and they can pull some amazing things out of the bag
<SNIP> you might get your dream house after all

Best of luck

From experience some alternative materials may be a cheaper option on paper. The truth is it totally depends on your experience and what free labour you can get. But don't kid yourself, if you can afford to take the next year off to supervise and get your hands dirty, then all power to you. Otherwise build a smaller house! We are still building silly sized homes in this country!

Straw bale or hemplime may be options for you, but a clever designer could knock 20%+ of your footprint and offer you passive standard for your budget.

beyondpassive

Ideally you would use a 220 cellulose fill stud with softboard in the cavity and as roof sarking board. Block outer leaf. A cheaper but less sustainable option is to use Polyiso in the cavity and use glasswool in lieu of cellulose with a back diffusion vapour membrane on the inside to let the timber sweat inwards in summer. Service cavity to roofs and walls. As others said, get a good designer to get the most out of your floor space and pay a bit more for the building fabric. Clever design of airtighness, thermal bridging and window installation will help keep the heat demand down. Designing a Part L 2011 compliant renewables based heating system is always tricky but well worth designing the house around the heating and ventilation strategy.

keru

Thanks BrianF. I'd be happy with smaller house but it took us 3 years to get planning. There is no way I am going through that torture (and expense!) again. The house is 210sqm so not crazy big considering there is 5 of us.
The house is on quite an exposed site so I wouldn't risk straw bales or hempcrete build because of the horizontal rain we get.

BryanF

keru wrote: »

horizontal rain

What finish is proposed on the timber frame?
I commend you for wishing to use natural Materials etc and wish you all the best. Don't take this the wrong way but I find people are all about the environment and voc free until they see the premium that such decisions bring ( unless as I said above you have time and free labour). Regarding insulation, at the end of the day mineral wool is cheap and recyclable, cellulose as BP suggests is a great option though a bit more expensive.
Have you done a Phpp (passive house) calc?

keru

beyondpassive wrote: »

Ideally you would use a 220 cellulose fill stud with softboard in the cavity and as roof sarking board. Block outer leaf. A cheaper but less sustainable option is to use Polyiso in the cavity and use glasswool in lieu of cellulose with a back diffusion vapour membrane on the inside to let the timber sweat inwards in summer. Service cavity to roofs and walls.

That's pretty much what we figured. First option being the favourite. I am getting a quote on the second this week so we'll see. I am not a great fan of membranes and had planned to use OSB with taped joints on inner face of wall for airtighness layer. Could that cause a problem with second option? Thanks for help btw!

juniorballyc

keru wrote: »

Thanks BrianF. I'd be happy with smaller house but it took us 3 years to get planning. There is no way I am going through that torture (and expense!) again. The house is 210sqm so not crazy big considering there is 5 of us.
The house is on quite an exposed site so I wouldn't risk straw bales or hempcrete build because of the horizontal rain we get.

Hi keru, we made our house smaller by 300sqft basically shrunk it from the outside but made few changes to interior to accommodate small size. It was deemed NOT a material change, so no change to planning. Got green light last week and hopefully turning sod next week. Also you will pay less contribution fees to council. Just a thought, it doesn't have to affect your planning.

archtech

keru wrote: »

Hi all. I am looking for advice to work out the best way to go about our build. I dreamt of a lovely TF passive house with natural insulation, but the budget wont allow it.

Considering you mentioned that the house has taken 3 years to get to this stage and house building costs(materials) have increased, how far off budget is the house now compared to when you started off the process. I 'm just wondering was your budget ever going to allow you meet your specification. Natural insulation has always been more expensive anyway.

BTW just because something is natural doesn't mean it is better for the environment or any healthier.

keru wrote: »

The house is 210sqm so not crazy big considering there is 5 of us.

its still 42 sq metres per person, with is a considerable amount of space, while small compared to many of the self builds of the celtic tiger days it is still a large house. A well designed house of 165 sq.m +/- 10% should be adequate for most families.

keru wrote: »

I am not a great fan of membranes and had planned to use OSB with taped joints on inner face of wall for airtighness layer.

Certainly in my opinion the way forward for timber frame is using OSB as part of the airtight membrane.

It would certainly be no harm to talk to the TF manufacturer's see what they suggest. TF is used quiet a lot in Germany/Austria in the construction of Passive/Low energy Houses and there's lots of good standard details developed to address thermal bridging. There are some TF guys here doing certifiable passive house TF kits which they claim are good value. Google will find them for you.

In terms of u-values and insulation, have you had a provisional BER done (and /or PHPP) and decided on an overall strategy to meet compliance with Part L.

keru

BryanF wrote: »

What finish is proposed on the timber frame?

We'll use blocks and leave a cavity. As to free labour, only my own time, no experience but not afraid of getting stuck in.
We are still undecided as to heating/DHW system. I'd like something economical and simple :rolleyes:. Thinking of stove with back boiler (access to cheap wood) and a MHRV, radiators in bathrooms. I don't really like underfloor heating ( slow response in changeable weather) and it bothers me to spend so much on insulation and still spend more in a whole house heating system.
The renewables requirements are a great idea but completely unreasonable if the house is so well insulated. I'd rather an "all in 1" solutions and am tempted by the thermodynamic system but the lack of actual performance data in our climate worries me. Any suggestions on cohesive system welcome!

keru

archtech wrote: »

Considering you mentioned that the house has taken 3 years to get to this stage and house building costs(materials) have increased, how far off budget is the house now compared to when you started off the process. I 'm just wondering was your budget ever going to allow you meet your specification.

Thanks ArchTech. To make long story short. Planning went in in 2008, when the banks were still landing happily. 3 years in Planning and oops banks not lending anymore. It took another year before we could get any loan approved! So Yes, if I was designing the house now, I would make it smaller but forgive me for not wanting to start it all again. The planners made it clear when I asked that any modifications would mean a new application and no way am I taking that chance.

archtech wrote: »

In terms of u-values and insulation, have you had a provisional BER done (and /or PHPP) and decided on an overall strategy to meet compliance with Part L.

That would make sense instead of me running in circles! Any idea on how much this consultation would cost and who to ask? Energy consultant or just a BER person? I was not blown away by engineer input on that subject but I guess it doesn't have to be his area of expertise or should it?

BryanF

keru wrote: »

We'll use blocks and leave a cavity. As to free labour, only my own time, no experience but not afraid of getting stuck in.
We are still undecided as to heating/DHW system. I'd like something economical and simple :rolleyes:. Thinking of stove with back boiler (access to cheap wood) and a MHRV, radiators in bathrooms. I don't really like underfloor heating ( slow response in changeable weather) and it bothers me to spend so much on insulation and still spend more in a whole house heating system.
The renewables requirements are a great idea but completely unreasonable if the house is so well insulated. I'd rather an "all in 1" solutions and am tempted by the thermodynamic system but the lack of actual performance data in our climate worries me. Any suggestions on cohesive system welcome!

I don't understand the use of a light weight timber frame with block outer leaf. Surely if your budget is tight then block cavity block is cheaper? To reach passive levels that is.
You have a source of wood, so a Gasification boiler is my preferred option, their expensive and require a thermal store, but there is no need for any other system. You could then just plumb for solar, not for the regs, but to offer you a future option of summer hot water.

kyeev

keru wrote: »

We'll use blocks and leave a cavity. As to free labour, only my own time, no experience but not afraid of getting stuck in.
We are still undecided as to heating/DHW system. I'd like something economical and simple :rolleyes:. Thinking of stove with back boiler (access to cheap wood) and a MHRV, radiators in bathrooms. I don't really like underfloor heating ( slow response in changeable weather) and it bothers me to spend so much on insulation and still spend more in a whole house heating system.
The renewables requirements are a great idea but completely unreasonable if the house is so well insulated. I'd rather an "all in 1" solutions and am tempted by the thermodynamic system but the lack of actual performance data in our climate worries me. Any suggestions on cohesive system welcome!

I built a house in 2010.
Here are a few tips I picked up along the way.
Build a two story box... (faster and easier to build)
minimizes foundation footprint, minimizes roofing materials (as opposed to a bungalow).
You can also fully insulate the attic with a foot of insulation (as opposed to a dormer where you have great heat loss along the dormer windows).
Point your living space at the sun (south or south-southwest facing).
Use plenty of glass, double glazed or triple glazed on this entire wall if possible.
We only need the heating on from november to about march.
I am amazed at the heat generated on a cold day with sunshine. Thermostats can rise from 18 degrees to 23 even in winter months.
I have underfloor heating. It is so comfortable. There is a real difference between that and radiators. It comes on for 2 hours at 4.30. Temp rises to 21 degrees and stays at that temperature til the next day. Acts like a heat sink.

Mistakes I made:
I built a dormer because they wouldn't give me planning permission for a two story. I tried and tried to get a two story.
But no. They were more worried about aesthetics and the shape of my windows than making sure the house was properly insulated and energy efficient.
I put radiators upstairs. I should have put underfloor upstairs as well.
I put in way over the regs amount of insulation in floor, walls, roof.
I should have put in more...

keru

Thank God we got the 2 storey passed. But like I said it took 3 years. Plenty glazing to south and west very little to north. So far so good? May I ask what heats your underfloor?

keru

juniorballyc wrote: »

Hi keru, we made our house smaller by 300sqft basically shrunk it from the outside but made few changes to interior to accommodate small size. It was deemed NOT a material change, so no change to planning. Got green light last week and hopefully turning sod next week. Also you will pay less contribution fees to council. Just a thought, it doesn't have to affect your planning.

Could you possibly PM me about how you did it? When I rang about it last year they just fobbed me off.

kyeev

keru wrote: »

Thank God we got the 2 storey passed. But like I said it took 3 years. Plenty glazing to south and west very little to north. So far so good? May I ask what heats your underfloor?

An oil burner, a firebird c35, I think we spent about 900 euro last year on oil, but we like the house hot.