Category Archives: Design

Plumbing Design

Mains Water Plumbing

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.)

Gravity Fed Design


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.

This on demand system is used in the USA for closed systems and two companies have developed a solution. One is and The first solution costs around $660 -too expensive.

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.





Rainwater System

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.

DIY Rainwater
DIY Rainwater


The planned schematic of the rainwater system is shown below.

Rainwater Harvesting
Rainwater Harvesting

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.

Wiring (Internet/Ethernet/TV)

Ethernet (Internet)

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 ( 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. )

Ethernet cable

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.



PV (Photovoltaic)-Converting light to Electricity (Part I)

The PV Plan 

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).

Air Mass and PV
Air Mass

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.

Pyranometer for measuring Solar Energy (Sensor top left of image and Solar Panel under test beneath it)

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.

Solar Energy

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.

Solar Power example

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

Solar Sunshine
Solar Irradiance Level examples over a 10 minute period.

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.


Wiring System (Lighting)

Lighting Control System

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.

Standard Wiring
Standard Wiring-230 Volts power cable at all light switches
KNX System-No direct connection from the switch to the light


Wooden Glulam (Week 3-5)

Work progresses on the wooden frame. As other self builders attest at certain times in a self build project the build moves quickly. This is one of those times.Self Build

Overview of Self Build



Elevation-View End View

 Side View Above


Living Area
Living Area
Roof Overhang
Steel Fixings to ring beam

Side View


Panorama perspective curved view


Roof detail with wood fibre board layer

Inside View Living Area

Images courtesy of David Hughes

















Foundation (Services)

Plumbing Services

A few notes that may be helpful to the self builder when planning the services such as sink waste, cold/hot water feeds, toilet services. The layout of the foundation services necessitates the early planning of bathroom layouts and even the choice of toilets and shower outlets before the floor slab is poured.

Foundation Services-White pipes are electrical services.

We visited a local bathroom showroom and we were informed that there are a few different types of toilet systems and they require a different pipe outlet location in the floor to ensure that they will fit. One has also to be sure that the layout of the bathrooms and toilets are what you want before the slab is poured.

For the shower outlets one has to decide between the use of trays or a walk in that is tiled flush with the floor or other finish. This will necessitate different floor slab preparations.

Another factor to keep in mind is that showers or sinks that are lightly used may dry out in the pipe trap resulting in unwelcome smells. I am trying to locate a unit with a larger water trap.

For sink outlets waste pipes it is beneficial to have these mounted in the walls so that different arrangements can be facilitated later on. This necessitates the slab pipework being brought up in the centre of the partition or in the service cavity. I have tried to keep all these inside the airtight membrane.

Kitchen Services

These need a special mention as one has to consider a duct for power cables if a kitchen island is used, water drain outlets for dishwasher etc and a cold water feed for a sink. It is practical to have the water main feed coming into the kitchen first before branching to other locations around the house. (This is more than likely the place one expects to switch the supply on/off) . Consider the grease trap outlet location also as they are substantial in size.

Electrical Services

In relation to electrical cables entering and leaving the house one needs to plan for cable ducts to garden lighting, main electrical supply (using special red ducting), rainwater harvesting cables, power for central vacuum unit if mounted outside the house, telephone line, broadband cables, power for outside shed if applicable, control wiring for services in plant room if situated outside, CCTV/alarm cables if applicable or a plan for these. I feel it is better to put the ducts in now as any unplanned cable changes in the future will affect the fabric of the building. My preference was to use a single 40mm duct for each cable with large sweeping bends for the electrical services. I feel it will be easier to ensure an airtight/rodent/insect seal with heat-shrink tubing on each duct.

Foundation Services Layout



Separate 40mm ducts for each electrical service.

HRV Drip

The HRV unit may also need a water condensation drip outlet. For this I plan to use a half inch heavy duty pipe that will go outside rather than plumbing it into the sewerage outlet.

Garden Water Supply

Because we plan to use a gravity based system the garden taps will be fed from inside the house using a 1/2 inch or 1/4 inch pipe installed in the foundation. One will feed either side of the garden.

Central Vacuum System

If this is being installed a special flexible PVC duct is required if the unit is situated outside the house.

Vacuum duct if placing a central vacuum outside

Performance Standard -Setting the Standard

The passive house software allows one to set your own performance standard by selecting how much energy (oil/gas/electricity) one wants to use to heat the building.

For example current Irish house builds that comply with today’s standard 2014 are estimated to use 100watts per m2 (subjective). The passive house standard if one goes for certification uses 10w per m2 (objective).

The real benefit for using the PHPP software is that the performance approach can be set by the home user. For example if I want to reduce my energy consumption to 1.5 litres of oil per m2 of the house size then I can set the software to a maximum of 15kwh per m2 for the year while maintaining a temperature of 20 degrees Celsius.

In a typical 3 bedroom house with an area of 100m2 the oil usage would be 150 litres a year.  With the PHPP performance software one can set the number of litres of oil (or gas etc) per year that your residential or commercial property will use to within a small margin of error. In other words you select the performance value of your build.

In summary the PHPP software takes into account your comfort and health (temperature and oxygen levels)  by removing high CO2 levels and VOCs and providing an even temperature throughout the house.

A Performance Standard

The Performance Standard

A performance standard is objective (quantitative) . One calculates the energy performance using software called the Passive House Institute planning package (PHPP). It calculates the energy gains and losses. Energy values for example are calculated from the number of people in the house, the solar gain, appliances, all types of losses such as the diameter of copper pipes feeding the hot water taps etc. This tool allows one to create a design for a new build or a renovation where the energy use can be quantified and set by the occupant.

Other solutions for managing building energy usage are in the majority rating systems. A rating system is subjective (nobody knows for sure how efficient it is or how much energy will be used). In Ireland the system is called BER (Building Energy Rating). In England they have BREEAM.

The Irish rating system is weighted towards adding on features such as a porch, solar panels, a heat pump etc., in order to get a high BER rating and it is subjective. One BER assessor may deem it an C2 and another a C3.

The passive house approach primarily aims to reduce and measure your energy consumption and only then do you add features such as solar panels or other heating systems.

While the two approaches exist the BER one is mandatory. What this means is that you could build a house to an energy performance standard that uses the lowest amount of energy in the world and fail to get the current Irish required BER rating.

My interest is the performance approach (using the passive house energy balancing software called PHPP) to design and build the house. As the old/new saying goes “if you can measure it you can manage it“.