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The main source of evidence for the efficacy of PAHS is anecdotal. As such, the capabilities of the PAHS system are largely unknown. | The main source of evidence for the efficacy of PAHS is anecdotal. As such, the capabilities of the PAHS system are largely unknown. | ||
Some critizise the technique, stating concerns including difficulty and expense of construction, moisture and lack of evidence.[https://www.greenbuildingadvisor.com/article/can-we-live-happily-underground][https://www.greenbuildingadvisor.com/question/new-earth-sheltered-pahs-construction] | Some critizise the technique (along with the earth shelter / underground house technique as a whole), stating concerns including difficulty and expense of construction, moisture and lack of evidence.[https://www.greenbuildingadvisor.com/article/can-we-live-happily-underground][https://www.greenbuildingadvisor.com/question/new-earth-sheltered-pahs-construction] | ||
==Notes== | |||
* The PAHS concept would appear to be appropriate for regions where the average temperature between summer and winter is high enough that it approximates comfortable room temperature. It would not seem suited to conditions where the average annual temperature was uncomfortably low, unless of course the passive effect is intended to be supplemented by another heating method. | |||
* The size of the insulation / watershed umbrella suggested by Hait is based on a calculated "deep earth constant temperature" of 7 degrees Celsius at 6 meters in Montana, USA.<ref name=Hait2013 /> However this appears to vary based on geographic location. For example anoth source gives the deep earth constant temperature as 8 - 11° C at 15 meters.<ref name=BSGwebsite>British Geological Survey (BGS) website [http://www.bgs.ac.uk/reference/gshp/gshp_report.html]</ref> | |||
==References== | |||
{{Reflist}} | |||
{{Solar navbox}} | {{Solar navbox}} | ||
[[Category:Passive solar]] | [[Category:Passive solar]] | ||
Revision as of 13:36, 4 January 2019
Passive annual heat storage (PAHS) is a building concept theorized to create a year-round constant temperature in an earth shelter by means of passive solar heating and a thermal battery effect lasting several months. It is claimed that an earth shelter designed according to PAHS principles would store the Sun's heat in the summer and release it slowly over the winter months without need for other forms of heating. This method was first described by inventor John Hait in his 1983 book "Passive annual heat storage: improving the design of earth shelters."
Description
The main component of PAHS is an insulated and waterproof "umbrella" which extends out from the earth shelter for several meters in all directions. The earth under this umbrella is kept warm and dry relative to surrounding earth, which is subject to constant daily and seasonal temperature changes. This creates a large heat storage area of earth, effectively a huge thermal mass. Heat is gained via passive solar in the earth shelter and transferred to the surrounding earth by conduction. Thus, when the temperature in the earth shelter dips below the temperature in the surrounding earth, heat will return to the earth shelter. After a time, a stable temperature is reached which is an average of annual heat changes in the external environment.
Another feature of the PAHS system is the use of a coupled heat exchange, earth tube ventilation system which provides cooled fresh air in summer and warmed fresh air in winter.
Evidence
Hait's book contained a limited degree of scientific evidence regarding the efficacy of the building system such as dynamic heat flow computer simulations and a few example buildings where some of the PAHS principles had been applied. However, as of the 2013 revision, the textbook still does not document a real world example of a PAHS earth shelter designed exactly as prescribed, or data relating to the performance of such a structure in the field.
The main source of evidence for the efficacy of PAHS is anecdotal. As such, the capabilities of the PAHS system are largely unknown.
Some critizise the technique (along with the earth shelter / underground house technique as a whole), stating concerns including difficulty and expense of construction, moisture and lack of evidence.[1][2]
Notes
- The PAHS concept would appear to be appropriate for regions where the average temperature between summer and winter is high enough that it approximates comfortable room temperature. It would not seem suited to conditions where the average annual temperature was uncomfortably low, unless of course the passive effect is intended to be supplemented by another heating method.
- The size of the insulation / watershed umbrella suggested by Hait is based on a calculated "deep earth constant temperature" of 7 degrees Celsius at 6 meters in Montana, USA.[1] However this appears to vary based on geographic location. For example anoth source gives the deep earth constant temperature as 8 - 11° C at 15 meters.[2]
