Is greenhouse interior much cooler if reflective inside?

In summary, the conversation discusses the potential impact of a reflective radiant barrier on the temperature inside a greenhouse. It is assumed that the greenhouse is initially empty and has a black concrete floor and insulated knee-high walls, with the rest of the structure being made of glass. The question is whether or not the interior air temperature would be significantly lower with the radiant barrier compared to without it, as the barrier would reflect some of the incoming radiation back out through the glass instead of being absorbed by the black floor and walls. The conversation also considers the potential impact of a large tank of water, painted black, on the interior air temperature if it is also intercepting some of the incoming radiation that would have otherwise been reflected out by the barrier. The focus is
  • #1
shane2
89
3
Let's assume typical 10' X 20' greenhouse for growing veggies is empty and is all exposed concrete black floor with solid black (opaque) insulated knee high walls all around. The rest of it is glass sides and roof.

Also, assume reflective radiant barrier was hung on those knee walls inside covering them all and laid across covering all the flooring, too, in the early cool morning. Ground and air inside and out all the same, say 70 degrees F.

Hours later the sun rose, outside air temperatures climbed to 100 degrees F, with the greenhouse fully exposed to the sun all day. No outside air exchange via doors or windows.

Question is; would the temperature of the interior air likely be significantly or appreciatively lower inside, with the radiant barrier coverings, compared to if there were no radiant barrier coverings at all?

I'm thinking it might, as more of the radiation penetrating is being reflected back out the glass instead of being absorbed by and warming up those black floor/walls where interior air is then in contact with them, too, being warmed up even more.

Any thoughts on how significant an air temperature difference there might be?
(Not inside and out, just interior air comparison with radiant barrier or without.)

One other question; same scenario above with radiant barrier, but room now has a large 200 gallon tank of 70 degree F water and it's painted black on the outside. It will be absorbing some of that radiant heat that would have reflected out and also some of that radiant heat that would have otherwise heated up the radiant barrier itself a little that it did not reflect and tank will also be absorbing some of the heat in the interior air itself, too.

Question is; do you think tank does much good cooling interior air that comes in contact with it when tank is also intercepting radiant heat that was otherwise destined to go back out the glass?

Thanks for any thoughts.
 
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  • #2
Let me just add, not looking here for techniques to keep a greenhouse cool, like shading, ventilation, etc.,
as I'm exploring a different application that would needlessly complicate the original inquiry of whether or
not internal air temperature is ever much affected by whether or not a radiant barrier was utilized in closed
system, like a sealed up green house, for my example.
 

1. How does the reflectivity of the interior affect the temperature inside a greenhouse?

The reflectivity of the interior plays a significant role in regulating the temperature inside a greenhouse. A reflective surface inside the greenhouse will reflect a significant amount of sunlight back out, reducing the amount of heat absorbed and keeping the interior cooler.

2. What materials are commonly used for reflective interior surfaces in greenhouses?

Some common materials used for reflective interior surfaces in greenhouses include aluminum foil, reflective paint, and mylar sheets. These materials have high reflectivity and can effectively reduce the amount of heat absorbed inside the greenhouse.

3. Does the color of the reflective surface matter?

Yes, the color of the reflective surface does matter. Lighter colors tend to have higher reflectivity, while darker colors absorb more heat. Therefore, using white or light-colored reflective materials will be more effective in keeping the greenhouse interior cooler.

4. Are there any downsides to using reflective interior surfaces in a greenhouse?

While reflective surfaces can help regulate the temperature inside a greenhouse, they can also cause uneven distribution of light. This can result in areas of the greenhouse receiving more or less light than others, which can impact plant growth. It is important to consider the placement and angle of the reflective surfaces to minimize this issue.

5. Can reflective interior surfaces be used year-round in a greenhouse?

Reflective interior surfaces can be used year-round in a greenhouse, but they may not be as effective during colder months. In the winter, the reflective surfaces may reflect heat out of the greenhouse, making it difficult to maintain a warm temperature. It is important to monitor the temperature inside the greenhouse and make adjustments as needed.

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