Dear WeatherCat victims of excessively hot summers,
There are plenty of locations where the summers are so hot that there is no choice to but to rely exclusively on air conditioning. However, some locations can get cool enough to bring your house back to a comfortable temperature before bedtime (probably the most critical time since we all need the sleep.) However, how cool does it have to get outside before you can cool the house sufficiently?
I created a very simply synthetic channel that I call the Exterior Cooling Potential:
-- Script: Outdoor cooling potential.scpt
-- -------------------------------------------------------------------------------------------------------------------
-- This AppleScript is designed to be loaded into WeatherCat synthetic channel feature to
-- continuously compute the difference between the exterior and interior temperature so monitor
-- when cooling an interior space can be cooled by opening the windows. When it is hotter outside
-- than inside, it returns zero.
--
-- Requires that the Param1 be set to the external temperature and Param2 set to internal
-- temperature
--
-- DISCLAIMER: This AppleScript and associated supporting materials is not subject to copyright
-- protection and has been put into the Public Domain as a public service. The author assumes
-- no responsibility whatsoever for use by other parties of its source code, documentation or other
-- materials, and makes no guarantees, expressed or implied, about its quality, reliability, or any other
-- characteristics. Any user assumes all risk and liability by attempting to use these materials in any
-- form whatsoever.
--
-- -------------------------------------------------------------------------------------------------------------------
set ExteriorT to Param1 -- Convert parameters into names that make code easier to read.
set InteriorT to Param2
if (ExteriorT ≥ InteriorT) then -- If it is hotter outside than inside, no way to cool the interior
return (0) -- Return 0 in those cases.
else -- Otherwise return the difference between in the interior and exterior temperature
return (InteriorT - ExteriorT)
end if
I have this parameter graphed like this:
The important part of this graph starts after 7:30 PM or so. You'll note that the graph starts climbing but eventually levels off and even drops a bit. What is important about 7:30 PM is that I had started a fan in the room where the Davis thermometer is located. With that fan running, you can see that the room only cools to about 9˚ F warmer than the outside air. You can see this on this graph that has both indoor and outdoor temperatures:
In the 7:30 PM and beyond time-frame the room cools down at about the same slope as the exterior temperature, but it remains substantially warmer than the outside air - by about 10˚ F. We have a whole-house fan and with that I can cool down closer to only 5˚ F more than the outside air, but that's still requiring the outdoors to be substantially cooler than you need to have the house in order to be comfortable.
With this in mind, if comfort is the goal, you need to keep running the air conditioner unless you have a reasonable assurance of exterior temperatures early enough and cool enough to cool your home to your target temperature. The naive notion of opening as soon as the outside temperature is colder than the inside may not result in a comfortable interior temperature, and as a result, an uncomfortably hot night's sleep.
Cheers, Edouard