february 15, 2010 02:33pm

Frog's chorus: Spring 2010 begins

Just outside the front door is a 3x4m rock-pool, fed by a spring above the house. Last year I counted more than 100 frogs during the mating season. The sound is terrific when they really get going.

This morning I counted about 20 frogs and the chorus has begun. This marks the official beginning of spring at Y Foel.

Posted By: MarkTiramani

5 comments | Comment

february 12, 2010 11:04am

Thermal mass steps up a gear?

A very sunny day yesterday. It temporarily pushed the internal temperature up to 23°C on the ground floor, which has happened before this winter, but yesterday it stayed above 21°C all the way to about 18:30.

Today there is a lot of cloud with the occasional extended sunny interval. At 11:00 the temperature is 21.2°C inside and 6.8°C outside. RH 73%/50%.

Surface temperature measurements of the slate floor and earth block walls on the ground floor show a 1-2°C increase over the last week.

The surface temperature of the union between the slate floor and the central earth block wall is 20.2°C.

The earth block wall core temperature (centre of ground floor at mid height) is currently 20.1°C. This is 2°C warmer than it was in mid November.

Well, we were warned it might take some months for the house to dry out, but it's our first house and it is hard to imagine just how long the drying and warming phase can last.

Y Foel has large thermal mass on the ground floor: Although the concrete slab is quite thin the slate floor is quite massive and covers 70% of the floor area. The slates are an average of 30mm thick and are laid on 20mm dabs of mortar that cover about 80% of the slate area. The earth block walls and lime render are 280mm thick.

I'll have to do the math soon and work out the mass and heat storage capacity.....

Posted By: MarkTiramani

48 comments | Comment

february 11, 2010 11:47am

Relative Humidity: spring?

Another cold snap but the sun is higher, the air drier and the house is drier?

I have been monitoring the relative humidity outdoors and indoors for about a month now. The outdoor humidity has been above 90% for almost the whole time, mostly 93-96%. The indoor humidity stayed between 50 and 56%.

Today at 11:45AM the RH is down to 56% outdoors, but indoors it is still at 48%. Outdoor temperature is 6.7°C and indoors 22.3°C. Warm but very comfortable for us.

It seems the house is doing a very good job of regulating the indoor RH.

But, I obviously must get hold of an indoor monitoring system that logs the RH and temperature throught the day for at least 4 points in the house...

Posted By: MarkTiramani

27 comments | Comment

february 03, 2010 01:10pm

Supplementary heating

It's a long, long story, but Y Foel was eventually built without any real supplementary heating system.

We do have a roughly 1,100W towel radiator in the bathroom. The idea was to provide a top-up by recovering heat via the MVHR extract in the bathroom.

However, in practice this does not work, for the following reasons:
(NOTE: I am aware that the numbers and calculations are simplified, and possibly a little naiive.)

There are 4 extract points in the house. The bathroom vent extracts roughly 25% of the total extract volume. Even with the bathroom door open the transfer of heat from the bathroom to other areas is minimal.

Therefore, the surplus heat energy extracted is diluted at a ratio of 1:3.

The bathroom gradually heats up but much of the energy is absorbed by the immediate surrounds and some is lost to the outside world.

If left to reach a stable state the heating effect via the MVHR would increase of course, but I am describing practical, useable operation.

So, for arguments sake let's consider a scenario where the inside temperature is 18°C. If the radiator is left on for 2 hours the temperature in the bathroom rises to 26°C. 75% of the extract air is at 18°C and 25% at °26C. After mixing the temperature of the air entering the MVHR's heat exchanger is roughly 20°C. At a heat recovery efficiency of 90% (NOT the overall MVHR efficiency with electrical and thermal losses) the supply air is warmed to roughly 18°C.

Even when the ventilation rates are increased the net gain is insignificant, because most of the heat from the radiator stays within a radius of about 2m. There are neither sufficient extraction volumes nor sufficient other mixing and circulation rates to raise the temperature throughout the house within a useful time period.

The above scenario is a simplified version of one experienced last November. The result is that even after several hours the air temperature does not show an increase in those parts the house farthest away from the bathroom.

As an experiment the other extract vents were closed and the cover of the bathroom extract was removed. The supply air temperature increased to > 20°C. However, further tests with a heater directly conected to an extract showed that ventilation rates of ~ 1 ACH were required before a temperature increase could be fealt within a reasonable time frame. However, the RH fell so much that the discomfort was unacceptable (sore eyes and dry skin).

This is an area where I believe the theory departs considerably from actual useability. At least for us, supply air heating on a cold day is not at all suitable. Use of a single heat source in an enclosed space is also counter productive, particularly if that source is on an upper floor and the main living area is below it.

Posted By: MarkTiramani

37914 comments | Comment

january 31, 2010 02:57pm

Warm books

Looks like the cold-storage books have more or less all reached 20°C or more.
Put a temperature probe into a box yesterday and measure 20.2°C.

Even though today has been mostly cloudy with snow showers, and 1-2°C, the house has not required any heating to stay ~ 20°C.

This was with a total primary energy consumption of 17kWh for the previous day.

At the same distance before the winter solstace (10-11th November) we lost 1.5°C overnight at an outside temperature of 4-5.5°C, but with an extra 11kWh primary energy consumption!

Although the comparison may be flawed due to unequal solar gains it is evidence enough for me that the house and contents have generally dried out over the winter, and the increase in contents has increased the thermal mass.

The mass increase has been mostly on the 1st floor, which was previously very empty. I think this has balanced the thermal absorption and probably improved it. Previously the slate floor and earth block walls had been very eager to suck up any energy they could from the air. Without any real solar gains in November the thermal mass on the ground floor was ruling the roost.

Posted By: MarkTiramani

89 comments | Comment

january 30, 2010 12:26pm

Heated storage?

Q. What is the largest energy consuming component of a flushing toilet?
A. The energy absorbed by the cold water used to refill the cistern after every flush.

Q. What is the largest one-off energy consuming element of a new Passivhaus if occupied at the beginning of winter?

A. Well, if you do as we did, and move all your books (and other "stuff" of similar density) out of storage and into the house in the middle of winter...

Over the last 2 weeks we brought the heavy stuff out of storage, where the temperatures were down to about 4-°C. Looking at the jump in space heating I estimate that we have used between 20 and 30kWh just to bring our stored "stuff" up to 20°C.

Specific heat capacity of books: 1.7/(g.K) ?

We have about 750kg of books, so that's roughly 1,275,000 J per °C. that's about 5.7kWh.... hmmm...

Posted By: MarkTiramani

6 comments | Comment

january 30, 2010 10:32am

A dusting of snow

Y Foel is on quite friendly terms with snow, ice, wind and rain; but it is in love with the sun.

Outside it's just above freezing, while inside the temperature effortlessly glided up to 21-24°C by 11:00.

Now the slates and earth blocks are soaking up the excess... as are the 750kg of books we just brought out of storage after more than 3 years... (see next entry).

Posted By: MarkTiramani

4 comments | Comment

january 28, 2010 12:42pm


The anger and frustration is indescribable.

After nearly 8 years of planning, designing and building, the UK's 1st PHI certified Passivhaus dwelling gets an EPC rating of "C".

This has to be one of the sickest home construction jokes to date.

Posted By: MarkTiramani

6 comments | Comment

january 28, 2010 12:17pm

Completion Certificate...... gasp....

After months of frustration, and at times despair, we have at last received the EPC for Y Foel, and with it the Building Control Completion Certificate.

I am finding it hard to grasp fully. It means we can now apply for our VAT refund, which we are very much in need of.

Posted By: MarkTiramani

458 comments | Comment

january 26, 2010 05:21pm

Winter 2009-2010 so far...

In two words: an education.

November was pretty tough for the UK in general, but the challenge for Y Foel was dense cloud cover.

The property is very well drained, being substantially covered in 1-5m of "badger sand". But the cloud cover was often so dense that we had minimal solar gains. The solar panels (hot water) produced negligable energy. The direct solar heat gains were very slight despite masses of S and SE glazing.

After record rainfall in November December brought the big freeze. Once again the local climate was milder than in some parts of the UK with a maximum depth of snow up here of about 65mm. The snow-thaw-snow sequences meant we could not drive down the hill for a couple of weeks. Days spent clearing and gritting turned to frustration as the next melt-freeze cycle hit.

The other major task was keeping our spring water system running. Spread over 5 x 1,750-litre tanks and a 45m height difference there are still exposed plastic pipes at 3 levels. At -11°C the ice in the top tank and pipes was so widespread that we had to collect water from the spring below the house for several days.

Then came the thaw and the badger sand cutouts for the saokaway and track started to collapse...

Posted By: MarkTiramani

8 comments | Comment