The greenhouse effect is well known to anyone who has entered his or her greenhouse (or car for that matter) amidst a blazing sun: interiors heat up considerably more than their exterior surroundings. The reason being that the energy of the sun’s rays heats the soil and plants within the greenhouse – plus the structure of the greenhouse itself – but fails to escape due to the heat-retaining design of the greenhouse. In this tutorial, we’ll show you exactly how to automatically cool a greenhouse with Eve Degree and a fan connected to Eve Energy. The same method can be used to circumvent the buildup of heat in attic apartments, sheds, or any other indoor space that is susceptible to heat retention.
Air exchange by ventilation
What is desired in a greenhouse during spring and autumn can be deadly for plants during summer, a period in which solar radiation exacerbates heat levels. Temperatures in excess of 30 degrees (86 F) damage or even kill most plants and, in a greenhouse, levels can reach upwards of 50 degrees (120 F). Usually, greenhouses equipped with windows and roof vents facilitate adequate ventilation when open. And plants save themselves from overheating by means of transpiration. However, on sunny days without wind, open windows and vents do little to facilitate air circulation. That’s why a fan, mounted one to two meters (3-6 ft.) from a roof vent, can mean the difference between luscious leaves and brittle twigs.
Measure and regulate temperature
With Eve Degree, we can measure the actual temperature in a greenhouse and keep track of fluctuating levels with the Eve app (the same can be done with Eve Room and Eve Weather). Now, with the help of two rules and two scenes, we can have Eve Energy automatically switch on a ventilator when Eve Degree senses a temperature in excess of 28 degrees (83.5 F), and switch it off automatically when the temperature drops below 23 degrees (73 F).
Two scenes for two rules
As noted, you need two rules with two scenes. For Eve Energy, create and set the scenes Fan On (activated by Power > On) and Fan Off (Power > Off). Test the two scenes manually to ensure that they work.
Rule for activating the Fan
To create the first rule, choose Scenes > Rules > Add rule. Select Add Value Trigger and Type > Temperature. Then activate Eve Degree. Under Value Trigger you will find Any and Specific. The easiest way is to set Specific, then More Than, and specify a value for the temperature, which in this tutorial is 28 degrees (83.5 F). Eve automatically creates a trigger with the value, Any, and the required value condition, which in this case is Temperature more than 28 degrees. Finally, select the scene, Fan On, and set a name for the rule, such as Ventilation On.
This workaround via a trigger (any change of the temperature value) with the value condition (temperature more than 28 degrees) is necessary in Eve because HomeKit currently does not allow value triggering with higher-/lower-than values in iOS 10. In the Apple Home app, such a rule cannot be applied at all. Eve makes it possible.
Rule for deactivating the fan
To ensure that the fan does not cool your greenhouse excessively, you need a second rule to deactivate it once the temperature drops to 23 degrees. This works analog to the rule for activating, in this case with Value > Specific, the condition Less than 23 Degrees, and the scene Fan Off.
Not only for your greenhouse
Anyone living in an insufficiently insulated attic apartment will also benefit from a similar setup, where windows are kept open or ajar, and a fan automatically facilitates air exchange for the purpose of cooling.
TIP: You can combine this automated setup with a humidifier to further regulate your indoor climate.
NOTE: Mobile air conditioning systems are not suitable for this setup as they require well over 3 kilowatts or power, which is beyond the load capacity of Eve Energy.
How it works
Eve Degree detects a (any) value change in temperature (in 1 degree steps) and notifies your iOS device or fourth-generation Apple TV. Your iOS device or Apple TV registers the notification and connects to Eve Degree via end-to-end encryption to ascertain the value change. Your iOS device or Apple TV then checks the value change to see if it affects a created rule with a condition (in our example, temperature exceeds 83 F). If this is the case, the corresponding scene – Fan On – is activated.
Still no HomeKit Notifications
HomeKit / iOS does not (yet) support notifications for temperature (nor humidity and VOC concentration), so you won’t receive a message on your iPhone from the Home app when your specified temperature is exceeded. We hope Apple will fix this soon. Until then, a workaround can be achieved by creating an additional scene that switches on a lamp connected to Eve Energy, or a Hue lamp, when your specified temperature is exceeded.