Draw Air From Underground Poipe for Cooling
By Bruce Nagy
What do the high-and-mighty, and lowly ground dwellers have in common? They both understand the simple physics of managing air temperatures, with help from Mother Earth. The Persian Empire was violently conquered and christened by 'Cyrus the Great' in 550 BC. He and his elite pals remained cool in the desert with help from solar chimneys and earth tunnels in their dwellings.
Similarly, prairie dogs are known for burrowing carefully engineered undercover channels that optimize air movement and minimize humidity and mould growth in their grassy below-form bedrooms. Both of these ideas are in a sense existence re-popularized during the present 24-hour interval, as earth-to-air heat exchangers, known more than usually every bit 'earth tubes.'
Elementary in design
Rob Blakeney of Local Touch Design in Guelph, Ontario, says, "An earth tube is a passive design concept, which works seamlessly with ventilation equipment like HRVs and ERVs.
In simple terms, it consists of a buried piping that draws fresh air through the ground to the home'southward ventilator. In winter, the world tube pre-warms the ventilation air and in summer it lowers the ventilation temperature besides equally removes moisture (humidity). An earth tube is platonic for our climate zone with cold winters but volition also provide cooling in the summer and shoulder seasons."
In the drafty, energy-intense buildings we've erected in recent decades, globe tubes might take been dismissed as irrelevant in terms of their pre-warming or pre-cooling load contribution. Just in very tight, highly insulated passive house buildings, the airflows are reduced, the arrangement temperatures are reduced, and the required BTUs are reduced. Those three factors impact modern pattern decisions and upset the assumptions of conventional HVAC load management.
Like many re-emerging ideas, thousands of world tubes accept been installed in Europe and elsewhere. However, they were not well received when introduced to Northward America around the early 2000s.
Bad installations or pointless applications here resulted in negative printing. Earth tubes were described as mould incubators that didn't yield many benefits. Things are changing. Earth tubes are being properly designed and installed – and helping with ventilation and heating efficiency.
Small systems for homes
Concluding twelvemonth, we reported on an earth tube-passive house combination virtually Goderich in Huron County, Ont. It included sensors and online monitoring, meaning more data is now available from the projection, and information technology'southward showing efficiency gains and stabilized temperature ranges. "With -15C outdoor air temperature (5F), we have measured +7C conditioned air temperature (47F) inbound the ventilator from the globe tube," says Blakeney.
Chris Lee, the homeowner, is also monitoring the data. Lee says, "There is always at to the lowest degree 10 degrees difference in the world tube intake air. In winter, intake temperature has never been beneath nil. I thought the ground would freeze, but even when it has been minus 20 in February, the incoming air is still above freezing. That's a significant efficiency advantage when you consider the passive house envelope."
"It is really working well in combination with the edifice'south ERV in winter for pre-warming," says Blakeney. "And in summer the Earth tube advantage is that they cool and dehumidify."
He saves more than than just what the Delta-T allows considering the earth tube means the temperatures are less extreme, allowing the heat pump to work in its sweet spot, and increasing the coefficient of functioning (COP) from somewhere to a higher place 3.0 to as high as v.0. And information technology provides good for you free cooling all summertime."
Install, monitor, test
Blakeney notes that AMVIC'southward residential Ecoair packet includes 180 anxiety (55 metres) of eight-inch anti-microbial pipe (sliver nitrate infused into high-density polyethylene) "plus all the necessary accessories including a pre-made stainless steel inlet tower, filters and condensate sump."
He also explains that sloping the world tube 2 per centum towards a condensate pit or sump pump prevents build-up of moisture and mould growth. "Minimum depth should be almost six feet where the basis temperature is pretty constant at 6-8C. It will provide upwardly to 4,500 Btu/h of free pre-warming in the winter as well as pre-cooling and dehumidification in the other seasons."
"I've also been keeping an center on mould and mildew," says Lee. "I opened information technology up and it was condensing in the tube within ii feet, so it was dehumidifying. I tested the bleed with a few litres of water and it took eight minutes to bleed. It seems to exist dry as a bone downwardly at that place."
Large project, large pipes
This yr Passive House Canada will agree its annual conference at the Scarborough campus of the University of Toronto (U of T), where the new Ecology Science and Chemistry Building incorporates geothermal heating & cooling, rainwater capture and an array of massive world tubes. These below-class concrete tubes feed fresh outside air into a ventilation unit in the basement. This works in sync with the ground source oestrus pumps and 60 geothermal boreholes, each about 689 feet deep (210 metres).
U of T is likewise using world tubes and the passive business firm standard together for 3 infill student/kinesthesia homes in downtown Toronto on Huron Street. In this example, a very old edifice with a basement was completely demolished and fabric removed, providing a more affordable opportunity to lay globe tubes while the new basement was existence constructed.
Earth Rangers project
Some other large earth tube system can exist plant at the Kortright Centre for Conservation, in Vaughan, Ontario, northward of Toronto. It's abode to the Earth Rangers, an beast protection pedagogy group, and another that organizes nature camps. It consists of nine tubes, each 69 feet long (20 metres), that warm wintertime air by as much as xx°C in the winter and cools the summer air past about 10°C. They permit the use of 100 percent fresh air inside the edifice, without incurring pregnant energy costs.
The tubes are supplemented by other corridor-shaped sections that practice the same job. They are left open up and fully accessible in the basement for ongoing inspections (and experimentation by National Renewable Free energy Laboratory).
The system is designed and so that incoming air is treated by UV filtering to foreclose pathogens (germs) from inbound the organisation. The tubes are sloped to ensure that condensate drains out properly. The same building uses a geothermal system and other clean energy elements.
There are at least 2 other projects using huge world tubes in Canada. 1 is the Vancouver Olympic Athletes Village. The other is the EPCOR Belfry in Edmonton. The tubes in the EPCOR Belfry are reported to be saving 1,473,994 kW/year in heating mode and 84,874 kW/year in cooling fashion, which translates to energy savings on the society of $50,000 per year. Not insignificant.
Another arroyo
Blakeney says those attending the passive house briefing in Scarborough volition too be studying brine loops every bit another style to precondition ventilation. It's like a geothermal field connected to a rut exchanger rather than a heat pump.
Some designs consist of a 300-foot length of one-inch plastic pipe placed around the foundation or nether the slab. A brine or glycol solution circulates through the heat exchanger upstream from the HRV. Brine loops reduce fears around air contagion, and, because it's liquid rather than air, they are more than efficient at moving energy.
Whether you're fearlessly leading a Persian ground forces into a bloody conquest, or designing buildings based on passive house principles, you can take advantage of the physics offered by Mother Earth. Yous tin get alee of the globe tube trend before it re-emerges from the underground.
Source: https://plumbingandhvac.ca/unearthing-the-lowly-earth-tube/
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