Building methods for passiv standard?

keru · 19-01-2012 03:24PM #1

We're about to start building our house and have for ambition to go without central heating. So up to passive standards but not worried about certification.
I have looked extensively at timber frame options but before we decide which building route to take I feel I should also look at the alternative of wide cavity wall method purely on a cost basis. In your experience is one more expensive than the other?
Is airtightness harder to achieve on concrete build?
I am also wary of man made insulation products on health and also environment grounds. Can anyone prove me wrong/reassure me? Thanks!

beyondpassive · 19-01-2012 03:43PM

keru wrote: »

We're about to start building our house and have for ambition to go without central heating. So up to passive standards but not worried about certification.

Technically you can heat a Passivhaus with a 3 kW heater, (think hairdryer left on 24/7 for the heating season) However in order to comply with building regulation ypu will need to provide a 'reasonable' proportion of renewables, perversely the lower the enegry demand the higher the proportion of renewables you need to supply. You can use PV but this is difficult to justify economically, so most homes use Solar Thermal Panels, which work with wet central heating systems. This can be delivered through the house by rads, underfloor or duct heaters

keru wrote: »

I have looked extensively at timber frame options but before we decide which building route to take I feel I should also look at the alternative of wide cavity wall method purely on a cost basis. In your experience is one more expensive than the other?

A good quality next generation timber frame with softboard, panelvent, 200mm cellulose fill, air tight smart membrane, 60mm insulated services cavity and plasterboard is ever so slightly more expensive than a 250mm silver bead filled wide cavity, but this is easily justified by having quick erection and enclosure and fast drying out. Its not a matter of comparing the cost of materials alone but the time and attention to detail needed for ultralow energy houses.

keru wrote: »

Is airtightness harder to achieve on concrete build?

Much of a muchness depends on the site crew, supervision and the quality of construction details and airtighness strategy. We've tested 0.22 on timber frame and 0.25 ACH's on wide cavity.

keru wrote: »

I am also wary of man made insulation products on health and also environment grounds. Can anyone prove me wrong/reassure me? Thanks!

Most polymer based insulations are pentane or co2 blown which is fairly inert. Styrene itself is a carcinogen but the risk is negligible, most of our food and drink is sealed in polystyrene and this isn't seen as a risk, although we are seeing elevated oestrogen levels in young people attributed to plastic bottles. I'd focus on the thermal and hygroscopic performance of natural materials and the higher thermal capacity, which give them huge advantages.

sydthebeat · 19-01-2012 03:51PM

beyondpassive wrote: »

..... We've tested 0.22 on timber frame and 0.25 ACH's on wide cavity.
.......

are those n50 / q50 figures...... or actually ac/h ???

beyondpassive · 19-01-2012 04:19PM

sydthebeat wrote: »

are those n50 / q50 figures...... or actually ac/h ???

They are n50 air leakage or air changes per hour at 50 pascals positive and negative pressure average tested. Both houses tested have volume numbers (ach's) fairly close to the envelope area numbers (in m3/hr permeability). So in this case you can take it that Q50 and n50 are are very close to interchangable. The q50 result divided by 20 is inputted into DEAP as the adjusted leakage at normal pressure.

BryanF · 19-01-2012 05:40PM

keru wrote: »

We're about to start building our house and have for ambition to go without central heating.

its a myth that a PassivHaus has no heating. As said above and elsewhere on this forum, designers still seem to oversize or install a backup heating system, just in case... the currently BER software also conflicts with the PH methodology and causes an over complication of what is meant to be a simple 'build tight, ventilate right' passive house philosophy

So up to passive standards but not worried about certification.

what do you mean by this? do you mean that whoever is overseeing your build will be contracted to build a 'passivhaus' to the prescribed heating load, Air change rate and KWH/m2/y? but just not pay the PH institute to check its complaince and issue the cert? or do you mean you'll employ a builder who will offer you cheaper options, renegue on the thermal bridge free detailing, not achieve the ACR, 1.5w/m2k windows frames and come in at roughly twice the PH standard? - still an admirable level of efficiency to attain but the term 'near passive' or 'Up to passive' should not be used - that's what the BER rating is for.

I have looked extensively at timber frame options but before we decide which building route to take I feel I should also look at the alternative of wide cavity wall method purely on a cost basis. In your experience is one more expensive than the other?

cavity block is cheaper on paper. there's no getting around it. i have looked into this and considered it in conjunction with the embodied energy/Co2 etc.. timber frame can be easier to control, cleaner, more precise, quicker to ensemble and get watertight but costs more and there's fewer skilled at it in Ireland + it can be hard (or more expensive again) to actually get local structural timber, environ racking board etc

Is airtightness harder to achieve on concrete build?

that depends on workmanship + specification, detailing and not taking the cheapest quote because its doubtful the know-how or time is budgeted for

I am also wary of man made insulation products on health and also environment grounds

my preference would always be for natural solutions. hemplime, rammed earth, straw etc can be a step to far for many who have grown up along side the concrete federation, so the best compromise imo is timber frame as it can be sourced sustainably and compliment natural materials, from cellulose, to hemp, to mineral wool depending on your eco ideals (it can also be designed/incorporate a breathable fabric which in-lieu of MVHR will help dissipate any harmful gases, water vapour etc)

Can anyone prove me wrong/reassure me? Thanks!

you a right to wary of man made materials, and the building fabric is an easy place to start. what you need to decide is where you feel is the acceptable compromise, as you will/ have compromised (as we all have).. expecting a baby, first things first: paint the kids room - creating a VOC /petrochemical nursery..
May i ask, if your chosen site requires you to get into your car for work, school, shop etc? then on the environmental grounds you need to start with a better site location...

keru · 20-01-2012 12:56AM

Thank you both very much for all that. It seems my original plans are not so out there after all?
By no central heating I mean we don't plan to put in conventional boiler plus plumbing for rads or underfloor heating. We plan on having solar panels and buffer tank with immersion back-up for summer hot water then a stove with back boiler to back it up in winter as well as produce some room heating and supply rads in bathrooms. I have heard of such a set up in a Construct Ireland article and it referred to this system as a "no central heating house". Coupled with "passive house features such as overall house U-values near 0.12, ACH below 0.6 and passive windows, and HRV it seems to be a reasonable and hopefully affordable way to get a very low running cost house even if it isn't a "passiv house".

beyondpassive · 20-01-2012 10:13AM

keru wrote: »

Thank you both very much for all that. It seems my original plans are not so out there after all?
By no central heating I mean we don't plan to put in conventional boiler plus plumbing for rads or underfloor heating. We plan on having solar panels and buffer tank with immersion back-up for summer hot water then a stove with back boiler to back it up in winter as well as produce some room heating and supply rads in bathrooms. I have heard of such a set up in a Construct Ireland article and it referred to this system as a "no central heating house". Coupled with "passive house features such as overall house U-values near 0.12, ACH below 0.6 and passive windows, and HRV it seems to be a reasonable and hopefully affordable way to get a very low running cost house even if it isn't a "passiv house".

Would you plan on putting some of the heat from the buffer then into a heating coil in the ventiltion.

A lot of people aiming towards passive, devise similar configurations, but as the design and Bill of quantities develop, they invariably stick in a boiler and a few loops of underfloor. Pricewise these represent a relatively small proportion of your heating plant, and it can be better to have them in and not use them than otherwise. There may come a time when loading the stove with seasoned timber and cleaning ashes once or twice isnt as much fun or isnt possible due to other commitments. Its also important in the event you had to sell as SAS has pointed out in another thread.

I would also note that the Passivhaus concept and MHRV are designed around supplying a fairly constant and consistent low grade heat supply to the house. Steep ramps in Heat at 6.30 and 4.30 are very old school, and waiting for

Then again if you work from home, or are a farmer it may work, just to relie on seasoned slow growth timber. You can cancel the Gym membership too, as they say timber heats you three times

BarneyMc · 20-01-2012 10:28AM

beyondpassive wrote: »

Would you plan on putting some of the heat from the buffer then into a heating coil in the ventiltion.

A lot of people aiming towards passive, devise similar configurations, but as the design and Bill of quantities develop, they invariably stick in a boiler and a few loops of underfloor.

Using the ventilation system to carry the heat around the house seems like a no brainer. What is the expense of getting the heat from the buffer tank into a heating coil in the ventilation? I would have thought it modest.

keru · 20-01-2012 10:48AM

If the HRV could heat the house out of the buffer tank hot water that would be the most logical. After all what is the point to go to the expense of going passive and then stick in a boiler and under floor "just in case"?
What I need to determine is the most efficient way to provide hot water to the house and yes, I agree, lighting the stove every day might get tiresome. I haven't looked at wood pellet burner. It can be automated can't it? Is the cost much higher? Unfortunatly budget is very very tight:o

sas · 20-01-2012 11:18AM

keru wrote: »

If the HRV could heat the house out of the buffer tank hot water that would be the most logical. After all what is the point to go to the expense of going passive and then stick in a boiler and under floor "just in case"?
What I need to determine is the most efficient way to provide hot water to the house and yes, I agree, lighting the stove every day might get tiresome. I haven't looked at wood pellet burner. It can be automated can't it? Is the cost much higher? Unfortunatly budget is very very tight:o

I'm going to put this as politely and as gently as I can. If your budget is very very tight, aim to borrow from passive\low energy principles, but forget about passive. You can't afford it. This is meant with your very best interests in mind. I'll pm you my contact details so you can test this with me if you like. In case you've not read much here, I'm finishing a certified PH build so am fully aware of the costs involved of going passive.

I've posted this multiple times before so here's the short version. My brother in law built a house exactly the same size (to the sq ft) as ours. Ours is a box, there's is a typical boom time design. They spent 100k less than us on the structure. They are getting by with approx 1k oil bills per year on that house. His missus likes the house tropical, believe me. MOeny wise they win hands down.

Think of it like this, assuming you are borrowing for the build.

100k for a low enery spec.
110k for a ph spec.

You're borrowing 10k over say 30 years, reasonable to assume you'll pay back 20k.

So in order to break even you need to spend €666 less heating the ph spec vs the low energy spec each year for the 30 years. I don't see it happening.

keru · 20-01-2012 12:58PM

SAS I agree with you. I never aimed at certified passive but only mean to follow the principles and find the best compromise between build costs and running cost versus servicing the mortgage.
But I would have to put some value on living in a healthier and more ecologically friendly building and I am ready to put a bit more money in the pot to enjoy that. After getting many quotes I am not convinced it is going to cost me that much more to build to the spec I outlined previously if we go direct labour for everything apart from the timber frame structure. Might be delusional but I am working as hard as I can to achieve that.

Do-more · 20-01-2012 01:49PM

BarneyMc wrote: »

Using the ventilation system to carry the heat around the house seems like a no brainer. What is the expense of getting the heat from the buffer tank into a heating coil in the ventilation? I would have thought it modest.

The problem with this approach is that the heat capacity of air is not great so there is a limit to the amount of heat you can add to the house in this way.

In another thread here somewhere MicktheMan pointed out to me that you can not heat the air above about 60 degrees C as the dust particles in the air will burn and you get a smell in the house.

Also if you have high humidity and high temps in the ducts it will be a breeding ground for all sorts of bugs.

I'm probably going to use duct heating in a limited way to ensure I maintain 16 degrees C in my bedrooms when it is below freezing outside and the calculations are that I will need to only heat the air to 32 deg C to do it. However even at that I am not fully convinced it will work as if I have the HRV on a low fan setting at night to keep the noise down it may not be moving enough air to carry enough heat. If it doesn't work I will put in some small thermostatically controlled electric panel heaters. The largest bedroom only needs 285W to keep it above 16 deg C when it is -10 outside so the energy consumption will be tiny over the full year.

@Keru I'm in a similar boat to yourself except a few months ahead of you, I'm due to break ground next month.

I'd echo what SAS has just said, I'm building a 200m2 dormer bungalow and will build to a low energy spec rather than passive.

I'm sure you could probably calculate it but my gut feeling is that there a point at around 22-25kW/m2/a which is the sweet spot in terms of capital costs vs. running costs. To make gains below around 22kW/m2/a there is a big ramp up in the costs involved.

You can for example pay huge money for the best outside doors and windows.

My house should end up around 22kW/m2/a or perhaps a little higher and all going to plan my running costs for heating and hot water will be under €400 a year.

I could easily spend another €30K-€50K to achieve a fully certified passive house as I would have to increase the spec of the frame, the doors, the windows and the HRV system, but my running costs would only drop by around €250 a year. So as SAS has already said it never pays off.

sas · 20-01-2012 01:49PM

keru wrote: »

SAS I agree with you. I never aimed at certified passive but only mean to follow the principles and find the best compromise between build costs and running cost versus servicing the mortgage.
But I would have to put some value on living in a healthier and more ecologically friendly building and I am ready to put a bit more money in the pot to enjoy that. After getting many quotes I am not convinced it is going to cost me that much more to build to the spec I outlined previously if we go direct labour for everything apart from the timber frame structure. Might be delusional but I am working as hard as I can to achieve that.

I went direct labour. I continue to be amazed at much certain things cost and how many of them I need e.g. soil pipe, ajs etc. it adds up so quick and this is where I believe most of us selfbuilders fall down and lack the knowledge of a builder. Naturally this is basic stuff to them. Worth keeping in mind.

Also, going direct labour on a house like this puts you responsible for the detailing. If you've time to learn this or already possess the knowledge, then great. Don't down play how much is involved. Don't assume your window company knows how to fit airtightness tape properly or will even be bothered to do it for you.

Good luck with it.

sas · 20-01-2012 01:52PM

Do-more wrote: »

I'm sure you could probably calculate it but my gut feeling is that there a point at around 22-25kW/m2/a which is the sweet spot in terms of capital costs vs. running costs. To make gains below around 22kW/m2/a there is a big ramp up in the costs involved.

What I've heard in general would agree strongly with your numbers here.

keru · 20-01-2012 02:14PM

Newby question. Do you get the heat demand values for your house from the PHPP software? If yes how do you get this done? do you have to go through some energy expert and what consultation cost can one expect?
I feel that I am shooting in the dark!

Do-more · 20-01-2012 02:33PM

keru wrote: »

Newby question. Do you get the heat demand values for your house from the PHPP software? If yes how do you get this done? do you have to go through some energy expert and what consultation cost can one expect?
I feel that I am shooting in the dark!

Yes Keru the basis for all my calculations are taken from PHPP but recently I have also had a heating engineer who is Passive house institute certified run over all the calculations and do individual calcs for all rooms.

You are probably looking at about €1,000 to get a PHPP or if like fclauson on here you like working with spreadsheets you can buy the PHPP software for about €150 but it's a very steep learning curve to use it without proper training.

keru · 20-01-2012 02:59PM

Thank you. Much to learn yet!:)

Eoghan Barra · 20-01-2012 04:07PM

Hi Keru,

You don't mention whether your house was designed from the outset with passive in mind. Is most of the glazing towards the south, east and west? Is the design compact in shape, or more complex? Is it split level? Do you have such things as dormer windows and rooflights, which let out a lot of heat? Etc etc.

Anyway, whatever the answers are to those questions, it's still worth striving for as low energy a house as possible.

Like yourself, I am on a tight budget and am aiming for a passive standard build without certification. I also have a lot to learn, but here, for what it's worth, are a few bits of advice:

1. Go direct labour; you'll have a few headaches but a neighbour who's just finished building his (standard) house reckons he saved 50-60k that way.

2. Use wide-cavity construction; the materials are relatively cheap, mostly available locally, and the methods are familiar to the local tradesmen who'll be doing the work. I'm using 200mm of rockwool fullfill, which costs about €7/m2, as opposed to about €100/m2 for external insulation, for example. Granted, there is another leaf of masonry to build, but it's still going to work out way, way less. My inner leaf will be of thermal blocks for better decrement delay and the wall ties will be glass fibre, which have a conductivity 100 times less than steel without any reduction in strength. This set-up should give a u-value of around 0.16 or less.

3. Save elsewhere but get the best windows and doors in terms of energy performance you can afford (i.e. low u-value, high g-value, very well sealed etc). Shop around for them too.

4. Look at insulated foundations; they are a little expensive but you can save a lot if you put them in yourself. Otherwise, pay particular attention to how to reduce the thermal bridge where your inner leaf passes the floor insulation. There are products available such as Marmox thermoblock to help deal with this (I have never used these and have no connection with the company).

5. Read past threads on boards and other forums, you'll learn a lot from other peoples' experiences (I did); check out the Denby Dale Passive House on youtube: they made a series of about 10 videos about building the house, all explained by the architect with diagrams etc in a very clear understandable way. You may not want to imitate everything they did but I found it quite helpful.

Hope that's of some use to you.

sas · 20-01-2012 04:42PM

Eoghan Barra wrote: »

s.
3. Save elsewhere but get the best windows and doors in terms of energy performance you can afford (i.e. low u-value, high g-value, very well sealed etc). Shop around for them too.

I would highly recommend you shop around too but only with Irish Manufacturers. I've heard nothing but grief (my own experience too) of dealing with Irish agents for foreign windows.

fclauson · 20-01-2012 05:01PM

sas wrote: »

...... I continue to be amazed at much certain things cost and how many of them I need e.g. soil pipe, ajs etc. it adds up so quick .....

We used a QS - may seem expensive when you pay their bill but its the best money ever spent on a build - and made comparing the building quotes very very easy

sas · 20-01-2012 05:05PM

fclauson wrote: »

We used a QS - may seem expensive when you pay their bill but its the best money ever spent on a build - and made comparing the building quotes very very easy

Yeah, in my ignorance in the early days of our build a QS was an extravagance of the wealthy!

BarneyMc · 20-01-2012 05:38PM

Eoghan Barra wrote: »

I'm using 200mm of rockwool fullfill, which costs about €7/m2, as opposed to about €100/m2 for external insulation, for example. Granted, there is another leaf of masonry to build, but it's still going to work out way, way less. My inner leaf will be of thermal blocks for better decrement delay and the wall ties will be glass fibre, which have a conductivity 100 times less than steel without any reduction in strength. This set-up should give a u-value of around 0.16 or less.

Eoghan, would you mind sending me a PM with the manufacturers of the Rockwool, thermal blocks and wall ties you'll be using?

Thermal blocks and glass fibre wall ties are super expensive unless I'm mistaking? Thanks.

Eoghan Barra · 20-01-2012 06:21PM

Hi Barney,

Rockwool fullfill Cavity Batts from Insulation Distributors Ltd, Dublin

325mm Qwik-fix wall ties from Coghlan engineering, Tullamore; €1.06 each incl. VAT & del.

alphatherm 140mm thick blocks from Acheson & Glover in the north, about €1.30 each + VAT

I have no connection with any of these companies

Do-more · 20-01-2012 06:58PM

Eoghan Barra wrote: »

4. Look at insulated foundations; they are a little expensive but you can save a lot if you put them in yourself. Otherwise, pay particular attention to how to reduce the thermal bridge where your inner leaf passes the floor insulation. There are products available such as Marmox thermoblock to help deal with this (I have never used these and have no connection with the company).

I don't know if there is a similar system available in Ireland but this is a section of the insulated foundation I am using on my build here in Sweden.

The element I have circled in red can be set at any position to increase or decrease the width of the ring beam and form a thermal break to the main slab. This effectively eliminates any cold bridge in the slab.

Another thing they do here in Sweden and something to consider if you are on a tight budget is to fit double doors on your outside doors, so one opening out and one opening in so you can effectively increase the u values without huge expense. If you put a bit of thought into the design you can have the inner door open and chocked out of the way for much of the year and only have it in use during the heating season when it's most effective.

BarneyMc · 20-01-2012 09:14PM

Do-more wrote: »

Another thing they do here in Sweden and something to consider if you are on a tight budget is to fit double doors on your outside doors, so one opening out and one opening in so you can effectively increase the u values without huge expense. If you put a bit of thought into the design you can have the inner door open and chocked out of the way for much of the year and only have it in use during the heating season when it's most effective.

So when you open the outside door you're faced straight away with another (internal) door? It's a bit like a 6 inch lobby? Sounds simple but effective!:D

beyondpassive · 20-01-2012 11:47PM

Eoghan Barra wrote: »

Hi Barney,

Rockwool fullfill Cavity Batts from Insulation Distributors Ltd, Dublin

325mm Qwik-fix wall ties from Coghlan engineering, Tullamore; €1.06 each incl. VAT & del.

alphatherm 140mm thick blocks from Acheson & Glover in the north, about €1.30 each + VAT

I have no connection with any of these companies

We've been using Silver blown bead in cavity

Vartry Eng Stainles steel wall ties

and Quinlite B3 or B5 for footing wall plate.

maybe someone could give the unit prices for these

kboc · 21-01-2012 12:07PM

beyondpassive wrote: »

We've been using Silver blown bead in cavity

Vartry Eng Stainles steel wall ties

and Quinlite B3 or B5 for footing wall plate.

maybe someone could give the unit prices for these

beyond passive,

how does this spec compare on cost against insulated rafts?

keru · 21-01-2012 01:04PM

I follow your thinking and it is very reasonable, however, how can you be sure it will only cost you €400 to heat your house in say ten or twenty years time? The way the price of oil, electricity and gas has gone up in recent years doesn't bode well for the future. Unless you can produce your own energy instead of purchasing it surely it makes more sense to lower your need for it?
In conclusion, I believe, but correct me if I am wrong, that your figures do not give enough weight to the rising price of energy. How much weight to give it is the real question and probably need a crystal ball to answer that one!

keru · 21-01-2012 01:18PM

sas wrote: »

.

So in order to break even you need to spend €666 less heating the ph spec vs the low energy spec each year for the 30 years. I don't see it happening.

This is what i was refering to in my previous post. New to forums, I 'll get the hang of it yet!:P

beyondpassive · 21-01-2012 02:49PM

kboc wrote: »

beyond passive,

how does this spec compare on cost against insulated rafts?

I don't understand the question?, you can use wide cavity on a thermally broken rising wall or alternativly on an EPS raft (supergrund, viking, isoquick etc.) The raft has zero thermal bridging.(in fact positive psi for Passivhaus), but can be slightly more expensive than strip, but much quicker. I don't see it as fair to compare on mere material costs.

http://www.integrated.ie/wp-content/uploads/2011/08/EPS-rafts.jpg

Do-more · 21-01-2012 03:34PM

You can never be sure that the house will perform according to the estimates. A lot is down to the ability of your builders in build it properly. Sloppy build quality can make a farce of the best designed house.

Of course no one knows precisely what energy costs are going to be in 20 years time but the point that myself and others on this thread are making is that once you achieve a certain (reasonably low running cost) level of performance the cost of making further savings are no longer economic.

I personally take the approach of getting to a decent level of performance and when new technologies become available at an economic cost I will add them to the house to offset my energy demand.

For example I have almost enough roof space available to offset almost my house's total energy demand using solar PV panels at present efficiencies and thanks to a 35% grant available here in Sweden it's already on the borderline for it to be economic for me do so.

The cost for me to install that much capacity would be about €15,000 so of course it doesn't make economic sense for me to spend €30,000 to reach passive spec for the house which would only reduce my energy demand by less than half.

Hopefully new technology will come along which will increase solar PV efficiency and reduce the cost per kWhr generated. So when it is economic for me to do so I will probably go down that route and end up with a zero or plus energy house.

Building methods for passiv standard?

Comments