Seasonal Thermal Energy Storage and the Passivhaus – lessons from 5 years of monitoring

Our own Dr Colclough will be a speaker at the next internationalPH conference in Leipzig, Germany

Our own Dr Colclough will be a speaker at the 2015 International PH conference in Leipzig, Germany

Scandinavian Homes passive house in Galway with its solar installation will be presented at the International Passive House Conference in Leipzig 2015.

The conference will constitute a forum for the exchange of information regarding global trends in the field of energy efficient building. A wide range of subjects will be covered at the conference to be held on 17 – 18 April in Leipzig: besides the latest research trends, regional and community schemes, cost-effective solutions for residential and non-residential buildings as well as examples of retrofits and of the Passive House Standard implemented in regions with hot climates will be presented.          Congress-Center Leipzig, 17-18 April, 2015


Interntional Passive House Conference 2015 in Leipzig




Theme 6:   1000 ways to heat a Passive House / Dr Shane Colclough

This paper describes the measured performance of a groundbreaking domestic solar heating system with a Seasonal Thermal Energy Store (STES) which is used to meet the DHW and space heating requirements for a house constructed to the Passivhaus standard. Conclusions are drawn about the extent to which solar energy can assist in achieving NZEB in a Passivhaus in Temperate Maritime Climates, and the key lessons from 5 years of monitoring are reviewed.

DruckPassivhaus coupled with a solar installation of 10.6 m² solar array and associated 300 lit domestic hot water tank, 23m3 aqueous subterranean Seasonal Thermal Energy Store (STES) and HRV system was monitored over a five year period from June 2009 to date. Data was collected at 10 minute intervals, with more than 10,000 data points per day used to analyse system performance

High performance passive house with seasonal store of solar heat.

Hibernia 164 passive house built in 2005 with the solar collectors on roof, the seasonal store tank (STES) is underground to the left.

Contents; Key performance data is presented for the installation including

  • Heating demand versus PHPP predictions,
  • Solar fractions achieved,
  • STES tank temperature profile and development of subterranean “buffer zone”,
  • Insulation performance compared with predicted performance, and
  • Evolution of STES tank loss coefficient.

Conclusions The results of 5 years performance monitoring highlight the key factors required for performance optimisation of such systems. The recorded performance demonstrates the viability of solar thermal installations in helping achieve NZEB when used in combination with a low energy dwelling constructed to the passivhaus standard in a Temperate Maritime Climate  – Dr. Shane Colclough, Dr David Redpath, Dr Philip Griffiths, University of Ulster, Newtownabbey, Northern Ireland, BT37 0QB.

PHI Professor Wolfgang Feist

The very first timberframe passive house in Ireland is soon celebrating its 10 year. Thousands of interested people from all over the world has visited Scandinavian Homes super passive house during the years. Dr Colclough and University of Ulsters research on large solar-system connected to a seasonal store in a passive house has been recognized globally and the findings has been presented at many international conferences.

The house in Galway is still open for interested public, check out for dates.

International Passive House Conference where 5 years of reseatch on Scanhome's solar passive house is presented.

International Passive House Conference Center Leipzig where 5 years of research on solar passive house is presented.

Read more about the 2015 passive house conference in Leipzig here:



Jim, who recently hosted International Passive House Days / Near Zero Energy Buildings – open days in his home, came up with a few pertinent questions. I am sure he is not the only one having thoughts about these issues…. Jim wrote:

Lars, We had a successful weekend for the passive house open days. Over 20 people came to visit. A couple of questions came up that I could do with an answer to:

—Jim: Why would you install a stove that draws air in from the room rather than a sealed unit with a balanced flue to the outside?

Passive two-storey house participating in International passive house open days and Near Zero Energy Buildings open days 2014

Passive two-storey house participating in International passive house open days and Near Zero Energy Buildings open days 2014

—Lars: I see no reason for separate air-supply if that is what you mean. It draws in cold air to the house with constant heat-losses as a consequence. It is difficult and time consuming (costly) to install a cold air supply. And hard to get to fit right onto the stove. The only time needed is at start up of fire when the draft is weak before the heat builds up in the flue/chimney. Our Swedish HRV-units have a function called “fire” that reduces the extract air for a few minutes to let the drag in the chimney build up when the fire is being lit. I have however no personal experience of this trick, for me it has always worked well without that. Another simple solution is to open a window a little for a minute or two while the stove is lightened.

—Jim: Why not install an extractor fan that recycles the air back into the room ?
—Lars: No, this is a very bad idea with all the grease and dirt coming from a kitchen extraction fan. The closest thing is our small HRV unit by Luftmiljö AB. This is only for smaller houses and apartments where the HRV unit is installed above the cooker in the kitchen and is integrated with the cooker-hood. There are still two outlets so that the dirty air is never mixed with the recovery-process.

—Jim: What is the issue having a smaller water tank so that the solar panels heat all the water up more of the time?
—Lars: Yes, a very good idea, a tall narrow 200 liter tank will heat up much faster and stratifies well so that higher temperatures are achieved at the top. The drawback is that the capacity is so small that the system would frequently overheat, boil and go into stagnation. You could only have < 1.8m2 collector area for a 200 liter tank to avoid boiling. I actually have this in our Swedish (now holiday home) house, with 1,8m2 vacuum-tubes, it never boils and gives all the hot water we need in the summer. But with such a small collector we get practically nothing in the late autumn, winter and early spring. To have a small tank and more collectors, you need to have a second larger tank as well, that can act as a sky white sun

Our current thinking after using small systems with 1.8m2 collectors up to large systems with up to 50m2 collector area connected to large seasonal store tanks:

a) Use 200 liter tank as tank 1 in utility room.
b) Use a larger tank as tank 2. This can be between 400 lit and 2000 lit. Should be well insulated and located in a dry insulated utility, basement or nearby garage.
This works as weekly storage/buffer/overheat protection. Dimension the collectors so that boiling and stagnation cannot happen.
c) Overheating and stagnation ages the components including the fluid and shorten the lifespan of the installation.
d) In Ireland we notice that 5.4m2 vacuum-tube collectors is the maximum collector (aperture) area to be used with a 400 liter single tank. In other words, we recommend a minimum of 74 liter tank volume /m2 aperture area to avoid stagnation.

Once a day in winter is all it takes to heat a passive house. With a stove you gain independence.

Once a day in winter is all it takes to heat a passive house. With a stove you gain independence.

—Jim: Everyone was generally impressed with the house and we hope they took the basic principles on board. We had a range of people from a couple living locally who were just curious to couples looking to build, those underway a bricklayer looking to expand his knowledge and an architect.

Hope it went well for you too

Regards, Jim

—Lars, It was good in Galway too, we had more than 30 visitors on the Saturday. Thanks you for your comments, we all need to share some of our experiences of modern passive construction. Thanks again, Lars


We like to share the figures we received from Velux about their high performance glazing for triple glazed roof-windows. They call it glazing variant 62 and 66:

Checking thermal performance of Velux triple glazed roof window in super-passive house in Galway

Checking thermal performance of Velux triple glazed roof window in super-passive house in Galway

Specification for 62 Variant triple glazed, enhanced noise reduction window: (from inside to out):  U-value = 0.81 W/m2° 4.38mm laminated with sound insulation foil, 18mm argon gas cavity, 3mm float with low emissivity (soft) coating, 42mm air gap 8mm toughened outer pane with anti-dew coating

Specification for 66 Variant  triple glazed window: (from inside out)  U-value = 1.0 W/m2°  6.8mm laminated inner pane with sound

Sica Super-maestic is used to further improve the seal around roof windows in Scandinavian Homes passive houses.

Sica Super-maestic is used to further improve the seal around roof windows in Scandinavian Homes passive houses.

reduction foil and low emissivity coating, 12mm argon gas cavity, 3mm Heat strengthened middle pane with low emissivity coating, 12 argon gas gap, 4mm toughened outer pane with easy-clean and anti-dew coating

From Velux company in Ireland: Sent: 05 November 2014 17:45


Take the opportunity to visit a passive house this weekend. Private people all over the world open their homes to show passive houses.  In Ireland we participate with our super-passive house in Galway.

Flyer 2014-10-31 PH in CelbridgeYou can find out where other houses are open and book a time here: Near Zero Energy Buildings open days (NZEB) website:

More info on Passive house association of Ireland here:

With us in Galway you do not need appointment this day, just show up between 11.. and 18.00 on Saturday November 8th.