West-Facing Windows

During summer heat-gain into homes is a big issue, especially when air-conditioning is used to regulate the temperature. It's far more efficient to prevent heat ingress than trying to pump it out afterwards!

Windows, of course, exhibit the "greenhouse effect" whereby light passing through the glass is converted to heat inside the structure. Heat, being long-wavelength, cannot pass through the glass as did the light and is so trapped - the greenhouse.

West and east-facing windows can be a boon in cold weather, allowing direct solar gain during morning and afternoon which can be a welcome brightener during gloomy winter weather. However these windows are prime culprits in admitting unwanted energy during hot weather.

Westerly windows are more noticeable as they admit sun during the afternoon when the house is already warm, the additional heat increasing internal temperatures to uncomfortable levels. However reducing heat gain from eastern windows is just as significant, helping to keep interiors cooler for longer.

Depending on site and geographical specifics, deciduous trees shading windows on east and west sides are very effective, also because they allow sunlight in during winter when the foliage has dropped.

Another option is external blinds which, with opacity of 80-90%, reduce heat load while still allowing some light through the windows. The impinging light heats up the blind but, being external, the energy dissipates without affecting the house.

Transfer Tanks

How to maximise your rainwater collection.

The most important aspect to maximising rainwater collection is the connected roof area - the larger the catchment the more water you're going to collect. However this can often be difficult to do because down-pipes are often located right around the house. One option is to have multiple rainwater tanks, although this can be expensive and often undesirable as tank location can be a sensitive issue (not everyone thinks they're beautiful.

Another option is having transfer units - small tanks located at the downpipes and then piped to the main tank. The transfer tank is fitted with a submersible pump complete with a float switch. As the tank fills up, the float switch rises and activates the pump which then pumps the contents to the main storage tank. Very simple.

Costs are quite modest compared to additional storage tanks - you can get a bilge pump for around $50 (I used a 300W Commercial Electric unit), a small tank for around $15 (I used a 60L Willow storage bin), and piping and fittings cost about another $50, depending on how much piping you need to connect to the tank.

So, for a modest outlay, you can increase your rainwater collection and maximise utilisation of your rainwater tank.

Optimising Tank Water Delivery

How to reduce your water pumping costs

Rainwater tank systems that are plumbed-in often use a pump to deliver mains-pressure flow, for household or garden use. Typically, the pump will be running at full power irrespective of the flow rate it's delivering, even if flow is restricted as in the case of filling a toilet cistern.

When used to water a garden there is usually no need to restrict flow. However, the fittings used in the delivery system may cause a significant reduction in flow rate. This may result in you taking more time to water your plants, and may also result in higher power costs due to your pump having to run for longer.

The first things to do to ensure your tank water delivery system is optimised is to ensure you install appropriate size piping from your pump to outlet or tap. A rough guide is to match the pipe size to the outlet of your pump. In my case the pump has a 1" outlet and I've used a 1" pressure pipe.

The next thing to look at is the size of the delivery system, starting with the tap itself. Conventional washer-type taps have a slightly convoluted construction, whereas ball valve taps provide a noticeably better throughput due the the straight-through flow of water. An additional bonus for garden watering, where I generally always want maximum volume, is the ball valve is fully open with just a quarter turn. Quick and easy!

Hose pipes are generally 12mm or 1/2", however 18mm versions are also available. The benefit here is they have more than twice the area of the the 12mm hosepipes, meaning lower velocities and therefore lower losses in transfer. However, note that the hose may  well be fitted with 12mm fittings, as these are the common fittings provided with most taps and hoses. To get the maximum benefit from your larger hose, dump these and get the 18mm fittings for the hose and tap.

The final element of the delivery system is the watering nozzle. You can get high flow units ready-fitted with 18mm connectors. Or, in my case, I drilled out my existing trigger gun to maximise the flow.

From a maintenance perspective, ensure that you clean the inlet filter. Due to the organic material that ends up with the collected water, these filters can get quite clogged. 

Removing these every month or so and giving it a good clean will ensure a good flow of water into your pump. The effect of a clogged filter will be most pronounced when your tank levels are low, resulting in very little pressure out of the tank.

Enjoy reduced energy watering with your pimped rainwater delivery system!

Aspirations for a Turbocharged Greenhouse

I'd long wanted to do something with the waste heat from our natural gas hot water service. Could this be teemed up with a greenhouse for improved results?

I had previously wondered whether, during summer, it would be possible to duct the exhaust through an absorption cooler to cool the interior of the house. Having done a bit of a search, however, I'd found nothing to suggest that this might be feasible, and the units used for refrigeration probably wouldn't work with the lower-temperature waste gas.

An different opportunity presented itself when we opened access to the flat section of our roof. It might be possible to locate a greenhouse on the roof and pipe waste gas from our adjacent hot water service. The appeal in doing this would be to add heat and carbon dioxide to the greenhouse, both beneficial to plant growth. The other input is water vapour, the other component of combustion.

My hope was that I might be able to be more successful in growing seedlings, something that I haven't had much success with in the past. Also perhaps be able to grow summer vegetables into the cooler months....

The greenhouse I bought was a small walk-in unit, approximately 2m x 1.8 x 0.7. The reason for the modest dimensions were due primarily to the difficulty of securing anything to the roof. Secondly, being primarily an R&D exercise, I didn't want to over-invest in what might be a green elephant.

For the turbo plumbing, I connected 100mm flex duct and suspended this with hose clamps off our bench structure.The final run of 4m tapered down from the inlet to roof height. The bottom of the duct in this run was punctured about every metre to allow condensation to escape. I discovered the need for this after the duct had sagged between the clamps, and found a substantial volume of water had collected.

I used a plastic drain unit as the vent into the greenhouse, and placed air bricks on the shelf above the outlet to act as thermal mass and help moderate temperature fluctuations.

Despite the condensation in the latter section of the ducting, there is still a lot of water vapour that finds its way into the greenhouse, so I added a low vent into the poly cover to allow some of the vapour to escape without losing all the heat.

At the business end, I connected the flex tube to the outlet of the hot water service and ran this up onto the roof and along to the greenhouse, a distance of about 8m. I wrapped the exhaust outlet with insulating tape before attaching the duct so as to thermally insulate the duct from the hot water structure - the duct obviously still gets hot when the burner is ignited, but the insulation means that the aluminium duct is not constantly drawing heat from the unit and losing this to the atmosphere along its length.

The energy injection into the greenhouse works well to keep it warm despite the wet wintry weather, and the water vapour keeps that the environment constantly humid. The combination works very well at germinating seeds, ensuring they don't dry out even if you forget to water for a few days. The celery seeds have just started to germinate so it will be interesting to see how these fare under the intense growing conditions.

I have found that thyme loves this environment, growing much more vigorously than I've managed in the garden during summer! The coriander grows very well although looks a little wan - perhaps too much growth and too little sunlight? The tomato plants don't do very well, the leaves being affected either by the high humidity or corrosiveness from the carbon dioxide. Having said that, the adult plant I transferred into the greenhouse is still doing a lot better than the one I left growing in the garden!

The system works well for seed-raising, as the moisture input ensures the seeds don't dry out during germination. Also the celery has grown exceptionally well, with good germination rates and strong growth. Tomato seeds I planted germinated well, but I have put these out on the roof because they don't like the aggressive medium of the greenhouse.