Floor laying continues with the Junckers System. The floor boards are 22 mm solid wood with a proprietary clip system. Each of the metal clips (shown below) connect each floor board. The clip type one selects depends on the expected humidity levels in the home. I used a soundproof underlay on the concrete floor. One can also nail this type of flooring.
Skirting Board Lighting
I started the design of the skirting board lighting that will be powered from a DC source (battery) connected to a solar panel. The idea is that this lighting would be on when it is dark and would also act as a lighting system if there was a power failure in order to minimise the use of candles.
The light output of this lighting would be equivalent to a candle and they are placed in bathrooms and corridors in order to allow one to walk around the house at night without switching on the main lights.
A first fix of how they will look is as shown below.
There are principally three methods it seems. One is the Supply method (used by manufactures) and this usually gives a higher efficiency value than the real world values. The Extract efficiency method is used to give a closer to real world value and then the passive house efficiency method which adds the following formulae to the Extract efficiency method.
Pel = real electrical power, W
M = mass flow, kg/h
Cp = specific heat of the air, kJ/kgK
The good news is that it appears if the HRV is certified to the Passive House standard then the difference between the supply method and the extract method is very small.
In the near future I plan to connect to the HRV unit I purchased and view the efficiency values.
The Passive House certificate shows the following
The most cost efficient unit I came across was the Airflow DV145 passive house certified unit for our 200 m2 house with an airflow capacity of 542 m3/h. I paid around €2200 for it. If one has a smaller floor area then more savings can be made by using a smaller unit. As a self builder technical support was important and their main offices are in the UK.
If one opts for a non-certified HRV unit a 12% reduction must be applied to the manufacturers specification . Some manufacturers might not renew the certificate each year so it is a good idea to ask if a certificate exists. The data must be entered in the planning software for the passive house. For those interested in the passive house planning software (PHPP) there are courses run in Ireland frequently so I would suggest that one does this 3 day course (typical) and usually one finds the software discounted on the course.
It is an enjoyable course where one can select your own pace (the first time I did the course I wanted to listen and learn rather than calculate the performance of our own home). One such place is http://www.passivehouseacademy.com/
There are two types of HRV units that I came across -Heat (HRV) or Energy (ERV). The ERV is used principally for recovering humidity and heat. I selected a HRV unit,
When selecting a HRV unit it appears that one of the biggest mistakes is to select a unit that is too small but still satisfies the current regulations. What appears to happen in the competitive world of quotations is that a unit that just ticks the box comes in as the best price.
In selecting a unit for our home I selected a unit that has a manufacturers capacity of 542m3/h where the floor area of our house is 205 m2. Currently the unit is running at 31% of its capacity and it is maintaining a CO2 (Carbon Dioxide) level of around 700 ppm when the four of us occupy it . I use a stand alone CO2 sensor to measure the CO2 in different rooms. (I have not commissioned the unit yet as the internal doors/glazing are not installed).
Another advantage of selecting a larger unit is that it can run more efficiently at lower speeds and generates less noise through the ducts or from the unit itself.
Some of the options from the manufacturer Airflow (my unit is the third from the right).
September 2018 performance (with no heating switched on yet).
The graph below gives an idea of how the HRV works when managing heat from the house and supplying fresh air. For the coldest days of the year so far (2 degrees at night-in September) I put the unit into summer bypass mode the next morning (take in outside air directly and pump it around the house) because the sun was shining that day. The winter sun is lower in the sky so solar gain increases in the winter (when the sun shines). The house is made of timber/glulam construction. The main thermal mass is the concrete floor at the moment soon to be covered by a 32 mm thick wooden floor so the response times of house I suspect will change. The floor and wall temperatures are approximately 22 degrees Celsius.
Example above of HRV in use in our home.
Sample Data in our home using Google Fusion to visualise the HRV data for a week in October. (see link below)
One can select the chart tab and visualise the graph.
Use the bottom graph to zoom in.
The data is from the 21 October to the 28 October 2018.
One storage heater rated at 1.7kwh was used for 5.5 hours a day off peak.
The storage heater was switched off for one day on the 23rd October.
The graph starts at midnight on the 21 October.
Each ref reading is every 10 minutes.
The CO2 reading vary between 480ppm and 700ppm when fully occupied.
All HRV units contain a maintainable part called filters. They have a number of functions.
Clean the air being pumped into the house, and
Keep the internal components such as fans, ducts and HRV housing clean.
One typically finds one coarse filter and one fine filter on the air supply into the house and a coarse filter on the extract air from the house before the extract fan. The coarse filter is typically a G4 and the fine filter is a F7 (Pollen filter). I installed a 400mm x 400mm G4 coarse filter at the duct inlet so that I could keep the main supply duct clean. It is a bit more effort to maintain this but it will hopefully minimise the maintenance of the duct.
Self Build air tightness test -0.22ach with a volume of 603 m3 @ 50 pascals.
When one is building to a performance standard the day of reckoning is the airtight test. The reason for this is that when one is pumping fresh air into the house using a Heat Recovery System, rather than relying on simple multiple holes in the wall, it becomes important to control where the fresh air is coming from and where the heat is going.
If air is leaking in or out around windows /doors/walls or other gaps in the building fabric then heat is lost and moisture problems in the form of mould can arise or else give rise to damage to the building fabric.
The pressure 50 pascals equates to a 20 mile per hour wind which is not too untypical in Ireland. So if one opts for the Irish building standard (a minimum standard) this equates to the air in the house changing/leaking 7 times a hour when a wind blows at 20 miles per hour. No wonder people block up the hole in the wall vents .
The current Irish building standard require 7 air changes per hour (ach) also called leakage at 50 pascals typically with no heat recovery system. As a guidance heat recovery manufactures recommend 3 Air leakages per hour to ensure that the heat recovery system can push fresh air into the house and recover heat leaving the house through its own system rather than through gaps in the building fabric.
The passive house standard for a new house requires 0.6 Air changes per hour (ach) at 50 pascals to ensure the heat recovery system works efficiently, ensure that occupants receive the correct amount of fresh air and minimise building fabric damage.
The passive house test differs from the Irish test because it must include pressurisation and depressurisation and use the volume as set out per Vn50 (EN13829).
Gavin O Shea from Greenbuild was hired for the job. He is certified/audited by the National Standards Authority of Ireland (NSAI).
The preparation for this entailed sealing all cable ducts and the inlet and outlet pipes for the Heat Recovery System. One also ensures that the shower and sink outlet traps are full of water. The overflow outlet for two water tanks were not sealed off. I did consider a duck valve but it was not in place at the time of the test.
The test using the Irish method gave a result of 0.181 m3
Gavin O Shea calculated that the equivalent size hole that equates to a result of 0.22 ach is approximately 65.25 cm2 (@50Pa) or a hole 81mm x 81mm if all of the leaks present in the dwelling were concentrated into one hole. That is about a tenth of an A4 sheet of paper.
The results of the air tight test can also help determine the selection of the Heat Recovery System. If the airtight test is lower then more options are available when selecting a unit.
From my research a passive house standard Heat Recovery Unit will cost more because it needs to be independently tested by the Passive House Institute using their test method. Heat Recovery manufactures have also the burden of putting the unit through national tests or international tests with the end result being the customer pays more. One has also the option to select a non passive house certified unit for a passive house but when calculating the performance value one needs to account for this in the PHPP software with a 12% reduction below the manufacturers performance claim.
If one wants to view certified Heat Recovery Units one can find and sort them at the following link. One can see for example at this link the capacity (Column- Air Flow Range) that these units have as it is important to select a unit that is oversized for your particular self build. I would compare it to selecting a mini car to tow a caravan up a hill compared to using a larger car. The small car will struggle from an efficiency and noise point of view while the larger car will be quieter and more efficient at the require flow rates. I will do a separate post on how I selected our Heat Recovery Unit.
Initially when researching the options available to plumb the house I came across two main methods- Pressurised/Closed or Gravity/Open. I settled for a gravity based system because of the simplicity, DIY, reduced parts and maintainability. If one can increase the height of the gravity tank the pressure will increase at the taps.
Below is a video of what a pressurised/closed system can do (if it goes wrong and probably very rarely). When I was researching pressurised systems I felt that there seemed to be different ways of designing these and providing the necessary safety levels. I do not like systems where there are potentially hidden failures (when a safety device is supposed to work and does not).
I also was hoping to use gravity to supply the showers but it is becoming more difficult to find a good choice of shower valves and shower heads that work on low pressure . The way around this to keep things simple is to install a shower pump in a central location for two of the showers (see below). One can then use a shower head that helps control the flow rate and keep the water use to a minimum.
For one of the showers I already have a shower valve and head that works well on gravity so I will plumb this separately directly from the tank (shower 3 in the layout below).
The plumbing layout for the house is shown below. (The toilets are fed from a separate gravity tank supplied by the rainwater harvesting system as shown on a previous blog.)
I am using Qual-Pex for the plumbing in the house. It varies in price so it is a good idea to shop around (The 1/2 inch varies from €70 to €200 for the same pipe). I ended up using 200 metres of 1/2 inch and nearly 50 metres of 3/4 inch and 25 meters of the 1 inch.
The overflow from the tank needs to be well secured or finished in copper to ensure that if the tank overheats the pipe will not sag/bend or cause a restriction.
The brass fittings are cheaper than the quick connect so I will use these. One needs a good plastic pipe cutter as using a hacksaw is not feasible. I used a Ridgid brand plastic pipe cutter and I am very happy with the quality.
With a plumbing design one needs to ensure that the size of pipes are no bigger than they need to be. One reason for this is that the volume of water in the pipe will cool down and one has to wait for this to run through fully before getting hot water at the correct temperature.
I calculated that 10 meters of 1/2 inch pipe holds approximately 1 litre of water and 10 meters of 3/4 inch holds 2.3 litres. This gives one an idea if a solution is required and the wait time.
The cold water pipes will be insulated as I am concerned that condensation could occur on the surface of the pipe.
I also tried to ensure that the number of connections/joints are kept to a minimum and I tried to place these only at accessible points.
Logistics of getting hot Water to the furthest points.
The kitchen sink hot water supply is too far from the tank so I may develop an on demand system that ensures hot water is available once certain taps are used rather flushing semi warm water down the drain and a one or two minute wait for hot water. Installing instantaneous heaters is not economical.
A way to solve this is only use one 12 volt pump and have a valve at each sink position. This pump will then feed into the gravity header tank rather than the hot water tank (I need to check the regulations) . I want to keep the plumbing connections and electrical devices to a minimum. The power to operate this can be a small solar panel charging a battery.
The plan is to develop a solution around the following -Measure the hot pipe feed temperature, Detect if the tap is going to be used and link this to controlling the pump and valve.
The only item that needs to be purchased is a 12 volt pump and a 12 volt valve and develop the control unit to suit the Irish regulations. I have started on the design of this. In the meantime I will install a third pipe in the bathroom and kitchen for the final solution.
As discussed in an earlier blog I will use the rainwater system to feed the toilets and one outside tap. I have started to install the pipework internally . This involves running a 1/2 inch pipe to each toilet. I note that the Drainage and Waste Water Disposal building regulations state that the pipe used must meet the following-“ for rainwater green / black / green bands and the words RAINWATER in black lettering“. I rang around and no one appears to stock this in Ireland. I note it is available in the UK. Instead I have marked the pipe with permanent marker in the above colours with the words RAINWATER. An image is shown below.
The planned schematic of the rainwater system is shown below.
I note that some rainwater systems top up the main tank in the ground if one runs short of water in the summer. I have opted for the header tank where I can manually top up this smaller tank with fresh water or let it automatically bring fresh water to the tank for the duration of the drought with the control unit I built. I feel that topping up the main tank with fresh water is more wasteful.
I am including an Ethernet cable connection to each room. The reason for this is that it provides a more robust signal and has a higher data rate compared to Wifi for internet use. I also ran an Ethernet cable to the TV and Stereo location as these technologies merge with the internet .
In order to install an Ethernet network one needs to select a central point to locate the switch/router and run a separate cable to each room from this position. It only took 3 or 4 hours to do this. The cost of the cable is low approximately €20 for 100 metres . The best value I came across is 305 meters for €49 (www.freetv.ie). There are a few types of Ethernet cable such as CAT5 and CAT6 and combinations of these. I installed the CAT6 un-screened cable as it offers a better performance than CAT5 and maintains the same type of connections that are used today.
The Ethernet cable looks like the following . The cores are twisted together in order to reduce noise. Terminating these cables is tricky (but the tools are low cost at around €10. )
A location worth running the cable to is the kitchen (never know what a kitchen appliance will do next).
For the TV (Terrestrial) one needs a 75 ohm cable and the satellite one requires a 75 ohm cable to match the LNB. The satellite connection needs to be kept short for the optimum signal ( I was told to keep it to less than 10 metres ). The TV 75 ohm cable can be any length. Be aware that there are low quality and good quality cables of the same type. One also needs to ensure that the 75 ohm cable bends on the cable are not below the manufacturers specification as this will increase the signal loss. A good cable manufacturer will state the minimum size of a bend.
A simple wiring diagram of the data cable routes are shown below. As the cable is very cheap it is a good idea also to install one near the front door and distribution board.
Below is my wiring diagram to ensure I do not miss something.
I really like the possibility of converting light to electricity. In the spirit of innovation I will simplify the PV system and reduce the cost by returning to using DC power directly from the PV panels. As I have no intention of transmitting power around the countryside this is another reason for staying with DC.
The passive house standard I feel helps in this approach by reducing the energy required in a house to a very low level which creates the synergy to make this leap for me to design a DC power heating system for our house.
Solar Background Information
The energy from the sun varies throughout the year due to cloud and the amount of air mass (AM) it has to pass through to reach the earth. When the angle of the sun is low in the sky the solar energy has to pass through more air which means less solar energy is available to convert light into electricity (example winter months).
When a PV manufacturer quotes the output power of their PV panel the international standard is to quote the output power at an air mass of 1.5 . An air mass of 0 is know as outer space where no air exists (AM0) . This is where the maximum energy can be captured if one lived in space. An air mass of 1 is when the sun is at its highest point in the sky (AM1) when on earth. The AM value of 1.5 is around 48 degrees off the highest point on earth.
Measuring the Solar Energy (W/m2)
In the winter months from tests I have carried out with my pyranometer ( a device that measures the solar energy-see below) the solar power I am recording with a data logger was between 0 and 400 watts per m2 (It can be higher on sunny days). In the spring/summer months the power can reach 1000 watts per m2 and more.
Harvesting Solar energy in the winter months for me is the priority which will entail the correct location and angle of the solar PV panel for the winter sun. The strategy is to try capture as much of the winter sun as possible by balancing the solar gain of the glass in the south windows of the house (part of the passive house performance phpp calculations) and supplement this with the DC (Direct Current) electricity from solar PV panels to provide space and primary heating etc. It is very noticeable at this stage of the build the real benefit of gathering energy from the winter sun through the glass. (See previous blog on performance data 23/05/2015).
In order to give an idea of the solar energy available I recorded the irradiance when the sun was behind a dark cloud (see image below). This equates to around 200 watts per m2 solar energy. When the sun came out from behind the cloud it reached over 1000 watts per m2 in the month of April.
Sun behind dark grey cloud is approximately 200 W/m2 of solar energy (above image). Most inverters start to loose their effeciencys at this point.
Sun behind dark grey cloud is approximately 112 W/m2 of solar energy on the typical overcast day. Most inverters would stop working at this level.
Below is an example of the changes that take place on a sunny/cloudy day in May
In the above chart one can see an example of how difficult it is for an inverter to keep working efficiently (they work efficiently from approximately 200 w/m2). The bottom line on the left is 100 watts/m2, The top line is 700 watts/m2 (click on the image to see more detail) . In the winter time values from around 50w/m2 to 200w/m2 are the lower limits and the upper limits are around 600w/m2.
Self Build Homework (Develop a DC powered Solar Harvesting Unit)
For the above I do need to find a way of maximizing the output power of the PV panels as the iradiance varies. For this I need to develop a simple black box (a small amount of simple components) that will match the solar energy created by the PV panels and maximise the output over the winter months. I am close to having a working prototype to see this in action (all tests look good so far ).
The equipment to be purchased for the above will be 4 solar panels and the mounting brackets. 4 solar panels will provide around 1 KW of power (max). This will cost around €1000. More groups of these will be added in the future. (If any one has 4 spare panels to loan so that I can test the control unit I am building – please let me know.)
In essence I plan to create what I call a DC Solar Harvesting Unit (DCSHU) that will have specific electric power functions around the house.
For the electrical wiring I plan to use a central control system called KNX for the lighting ( I will build in the flexibility to control power outlets from the switch positions in the future) . What this means is that the power for the lights will come from a central fuse/distribution board and the switches for the lighting will be independently controlled by an extra low voltage.
The reasons for selecting this KNX control system are:
to reduce the impact of interfering with the airtight envelope (as the cable is similar to alarm cable thus less wiring will need to be installed and more room functions can be carried out with one cable).
Extra capacity can easily be included in each switch position in order to allow for wiring changes in the future. (If a new light needs to be controlled from an existing switch no modification of the wiring, internal wall/ceiling structure or room re-decoration needs to take place).
Because the voltage is very low and DC (Direct Current) it will reduce electrical and magnetic fields and minimize the use of 230 volts AC (Alternating Current) from a health perspective.
Possible to use extra functionality already available in KNX such as timers/power down control (did you ever have an ESB power failure and one had to leave the house before power was restored only to find when you came back that items were left on such as lights or hairdryers etc.-with the KNX system one can configure the system to return everything to the off position when power is restored.)
When leaving the house one switch can be configured to turn off all the lights or turn on essential lights.
I became a KNX partner in order to purchase the software to design and develop a prototype before the build. There are other building control systems and smart systems but the KNX system is a world standard and an open standard for commercial and domestic building control. Most of the large electrical companies manufacture KNX products.
While the KNX system can manage the most complex building and smart home systems I will be using the most basic functions of the KNX system in order to keep costs under control and make use of the benefits as outlined above.
The sketch shown below might help to explain the difference between a standard wiring system and a KNX system.