Do we need PassivHaus?

[Bodidly]

I have done some reading on here but not really found this covered but if I have missed it please point me the way.

OK here is my thinking. Increasing levels of insulation have a ever diminishing returns for there costs. With the ever dropping price of PV and the relative good value of ETs at what point is better to spend lets say £15.000 less on the build and spend the rest on heat and electrical generation. I realise that this tipping point will change the further north you live and I am completely in favour of very well insulated houses but from my limited experience of the building industry it might be better to enforce the current standards before heading towards PassivHaus. For me I did not see the BCO between laying the concrete floor slab until completion. What got me thinking about this was reading a PassivHaus thread on here were many did not like idea of MVHR this might be an alternative  way.

I have never visited a PassivHaus and do not know how to do the figures so feel free to shoot this down.

Beau

[rondurrans]

A couple of links:- 

Airtightness in Dwellings - Prepare to be Sick in your Airtight Home: Is Tight Right for British Homes? http://comment.veetech.org.uk/index.htm

http://e-futures.group.shef.ac.uk/publications/pdf/153_Ventilation%20Indoor%20Air%20Quality%20Poster%20for%20Adorkor%20Bruce.pdf

http://www.leedsmet.ac.uk/as/cebe/projects/derwentside.pdf

http://www.energysavingtrust.org.uk/Publications2/Housing-professionals/Refurbishment/Sheffield-EcoTerrace-A-refurbishment-case-study

Dimitroulopoulou, C. (2011) Ventilation in European dwellings: A review. Building and Environment 47 (2012) 109 -125

Dorer, V. & Breer, D. (1997) Residential mechanical ventilation systems: performance criteria and evaluations. Energy and Buildings 27 (1998) 247 – 255.

Monahan, J. & Powell, J. (2011) A comparison of the energy and carbon implications of new systems of energy provision in new build housing in the UK. Energy Policy: January 2011, Pages 290-298.


Triltmand (2009) claims that ‘airtightness is not fail-safe’ and that the ducts used to supply and extract the air can be ‘virtual incubators for microbial pollutants…’ this opinion is reiterated by Dimitroulopoulou (2011) he found, when discussing ventilation rates, that ‘increased concentrations of poor indoor pollutants and exposure to health risks’ and that occupants understanding of ventilation ‘resulted in under-ventilated homes’. The NHBC (2009) suggest that maintenance of the system may be ‘inadequate’ and that this could lead to ‘…a build-up of dust that can be a source for microbes, chemicals and allergens in the indoor air’. Dorer et al (1997) established problems such as ‘commissioning…window opening behaviour…sealing of ducts and heat exchangers’ when reviewing mechanical ventilation. On the face of it MVHR seems like a good idea as long as the fans and heat recovery systems are efficient and more importantly the air permeability is less than 3 m3/m2.h, however when air permeability rates are below this a robust annual maintenance schedule is essential and must be adhered to, to ensure the health of the occupants is not compromised.

[MarkB]

There are a couple of good reasons why PassivHaus makes a lot of sense.

First, when you really need the heat there doesn't tend to be much daylight. If you recall last winter there were a couple of weeks of snow with consistent sub-zero temperatures. Unless you're going out to scrape the snow off your panels every time it snows you wouldn't get anything out of your PV. Even on a bright clear day, the amount of energy available to capture is low due to the low angle of the sun and the short day. You'd need a very big array to cope with the heatloss for a typical house even on a sunny day. I haven't done the sums, but I suspect that it is easily over 10kW. If you want to roll through the bad days as well factor in a few days heat storage (which will be massive) and an even bigger array.

Secondly, PassivHaus isn't just about energy loss - part of it is about comfort. High spec glazing means that the internal surface temperature is high and eliminates any risk of condensation. It also helps to reduce draughts.

[billi]

Mark


A 10 Kw PV for example does generate more energy , than a modern  house would need for heating and Electricity  seen over the year ,

[M]

Regarding PV and winter - recently been chatting with a nice bloke living in Essex. He got 13.5kWh's yesterday, and 161kWh's in December. I was shocked at the numbers so asked for more details.

He has a 3.9kWp 3.5kW inverter system, facing south in Essex, but crucially it's at 49deg. His system should be 30% better than mine (and is on a per annum basis), but it's only 10% better in June, and 200% better in December. I wasn't blind to the importance of panel angle, but till last week it simply hadn't dawned on me how important it was as a way of levelling off generation through the year. For a ground mount, I assume a steeper angle would greatly improve the amount of generation that could be consumed, via reducing peak differences.

Cheers.

Mart.

[brackwell]

Mart,
Thats right but the problem is that people are focused on FITS payments (a distortion of supply and demand) and for me the best angle 39 deg.     If there was not FITS i am not so sure that best bangs for bucks would be a vertical mounted system at floor level with a reflective surface in front.  Installation cost would be less, total output would be little different and would align better with winter/summer consumption.

Ron, 

A great link you gave  http://www.energysavingtrust.org.uk/Publications2/Housing-professionals/Refurbishment/Sheffield-EcoTerrace-A-refurbishment-case-study
At a cost of £45K that clearly was not the total cost by a long way and it begs the question why not pull down all solid wall buildings and start again.    I cant think of any other asset where we continue to repair and make do  when it should be scrapped!

Beau,

Nothing compares in value with insulation bearing in mind that if this is done at the time of new build it costs very little and if you get to the point where one can say remove the central heating system then its net cost could become nil.
I believe it is quite easy to become carbon neutral over the year but quite difficult on a day by day basis and therefore we once again get back to storage.   We dont need energy production plants but energy storage plants !

Ken

[clockmanFR]

Mart, Very true regards angles, And hence my design and manufacturing of 2off 1.5Kw PV Tracker units.

Beau, To me its the initial costs against savings on those initial costs. One thing for sure, buying in energy is going to become more expensive so I set the costs as present day.
I look for a cancelling out of installed costs against savings on energy at about 15 years.

However, its the initial costs that can rapidly climb if one gets the "Wallpaper Syndrome".

Very, very importantly for me its good design, that starts from an energy saving point of view, rather that the standard builders add on concept.
Good design and good material research can get prices significantly reduced, and further cost savings by using building techniques that are traditional or can be quickly understood.

Its a fantastic time for energy saving as Insulation products, PV, are in real terms at thier lowest prices that I have ever seen.
 

[rondurrans]

You will find another one here: 

http://www.energysavingtrust.org.uk/Publications2/Housing-professionals/Refurbishment/Oxfordshire-A-refurbishment-case-study-achieving-a-carbon-reduction-of-over-70-2011-edition

[brackwell]

Ron,

Another good one. It says that a 2.52kwp pv raised the rating from 70 to 79. I wonder if that implies a 4kwp would have raised it by 14

Thinking about it perhaps the gov idea to make people reach grade C AFTER including the fitment of PV is entirely doable and not that daft afterall.

Ken

[renewablejohn]

With the new CHP systems with 38% electrical efficiency and 72% overall efficiency Passivhaus will not be so important so long as you have room for the tracker which you need to optimize solar in the UK.

http://www.greenprophet.com/2011/04/2kw-solar-cell/

[billi]

Passiv house  ?

I think  important is to create a network  to get low carbon, low Grey energy intense  building material supply in place
And show people that modern living can be easily achieved  with natural building materials as well ....

Even better to use wood , paper, biomass, subsoil/clay  based products  to built  a modern house to store CO2  instead of  just looking  on the heating bill  or Energy rating calculator  .... and use energy  intense building materials  

[sam123]

Whole passivhaus religion based on the idea that building is so well insulated that it doesn't need any heating power. All heat is coming from domestic machines, peoples and so on. In "real" passivhaus, you don't need any heat pumps or expensive heating system, because consumption is so small, that direct electricity will do the job.

Bull sausage...my house has been build with year 2002 regulations (10cm EPS on floor, 20cm rock wool walls, and 40cm rock wool roof, 3 glass windows) and has GSHP + UFH.

New houses have pretty much double insulation and passive houses even more. Still even passive houses in Southern Finland can´t beat my consumption even they have 15-20% less heating degree days 

We had several passiv house projects in 2008-2009 and they promise measurements after a year, but guess what? Nothing ever showed up.

Answer is: No you don´t. Increasing insulation makes your house hot at summer, it doesn't warm your DHW, risk of bad ventilation (=sick house) increases and so on. In climate of UK-> 

[clockmanFR]

sam123,

Your comment, Answer is: No you don't. Increasing insulation makes your house hot at summer, it doesn't warm your DHW, risk of bad ventilation (=sick house) increases and so on. In climate of UK->  

That's my point about design, Uk wise passivhaus is seen as an add on to some awful standard design.

Personally with my bit, we do not suffer with bad air because we designed and raised the ceilings and made the rooms large giving natural convection time to function. Regards Hot at summer, I disagree with you there, if the building is designed properly, it does not get hot, ours in summer is cool, but you have to learn to manage your interior environment.
We only put the underfloor electric heating heating on, approx 1.4Kw total (runs on the Wind turbines) in the winter months, Mid Nov to April.

[Bodidly]

Wow lots to think about.

I don't know how to talk about this subject without using my own experience which consists of converting my barn and visiting another recent build.   

Barn conversion
I was working to BR 12th edition and intended to insulate beyond the regulations.  I used multifoil insulation on roof and walls, I believed at the time that this reached a U value of 0.2 in the roof (I think from memory).  It was not officially recognised for use in walls but I believed it would beat the required U value of 0.35.  We also have 50mm of PUR insulation between the rafters.  After a recent post on a green building forum the general consensus is that the multifoil is less effective than 50mm of PUR insulation.  I do not want to make this a debate over multifoil, I am just saying that if all those facts are true then our house is insulated below 12th edn requirements.

All the work was carried out meticulously and our annual energy use figures are 3699 kWh plus 6 cubic meters of logs.  The barn has a bad surface area to volume ratio: external dimensions of 22m by 5m and 1.5 storey running North South. 

I realise these figures are not remarkable but they seem to completely out perform other houses built to the same regulations and is well up there with some supposed "eco houses".  I suspect the difference relates to the care put into the installation of the insulation, but I don't know.

We also have 3.76kW PV system. Today this produced 11.3kW I realise this is an exceptional good day for winter but I think this install will almost match are annual yearly demand but not match the times of the load. So to be neutral over the year we need to match the energy of the 6m3 of logs as well.

I am trying to get to my point but I find it hard without the barn for a reference.

I have also done some wood work on a new extension nearby. I got to see the roof insulation and it had gaps everywhere but they had no intention of doing anything about these. I later went back to fit some skirting boards and there was a howling draft coming in and the room was hard to heat, this extension was built to stricter rules than the barn but was clearly worse. But both are passed by building control so I do not see any point in higher standards before the current standards are properly implemented .  I would like to add that I have nothing against PassivHaus it appears to be a very good goal but I am still questioning if the extra cost of building to such a standard particularly in the south of the UK is the best way to spend the extra money.

I do not know how much better the regulations are but lets say I had built the barn to these. So now lets say I only need 5000 Kwh total but don't  burn logs any more so I now need an extra 1000kWh to meet my annual electricity needs but I have saved lets say £8000 by not building to PassivHaus standard for this I can install another 4.0kw of PV producing maybe 3900 kWh. Now we have a summer surplus that the country can benefit from and in return the country invests in windpower which will have it's highest production in winter when my PV is not meeting my demand but overall the country has gained 2600kWh is this not better than PassivHaus?

Other than our energy figures the other numbers are at best a guess  but I have done this just to explain my point.

Thank you all for the input I know I have a lot to learn.

Beau

 

[billi]

thank you as well