DIY Light Proof Vents

DIY Light Proof Vents: Not That Complicated!

You’re growing hemp on your own and so far have kept them in the optimal conditions.

But you remember about them needing a light and dark cycle of about 12 hours. That gets you worried because there is plenty of light coming through the vents. And airflow is a must too.

You know the solution to this, so how to make diy light proof vents?

To make diy light proof vents, the simplest idea is using ducts. Because this lets the air pass through from the outside but blocks all the light. To do that, make a U-shaped turn using ducts and attach them to vents. Or you can use DIY flap-like structures using roof panels too.

Well, that’s just the basic idea. All of these need detailed instructions to be completed. And we’ve done exactly that in our article.

So let’s get going!

Why Are Light Proof Vents So Important?

When growing hemp you need to maintain temperature, airflow, and humidity perfectly. There is also a very important phase that hemp plants need. 

Hemp plants require a dark and light cycle of 12 hours to flower properly. Failing to maintain this 12-hour dark and 12-hour light cycle can damage the growth.

Making a greenhouse or grow tent dark isn’t that much of a problem. But you need ventilation to ensure proper airflow as well. Because both growth and water or air curing your hemp need airflow.

But when you allow airflow with darkroom vents, both ways you need to have openings. These vents can let in light. That is when there is light outside but your plants are in the dark cycle.

And that could totally damage the growth of your hemp. And that is why you need to have some sort of way to block out the lights without hampering the airflow. That’s why you need a light trap vent.

This is where you need the help of this article. DIYing a grow tent light trap isn’t as complicated as it might seem. You need to follow some basic ideas and you can easily make one for yourself.

So let’s see how you can make a diy light proof vent for yourself.

Make A DIY Light Proof Vent: Step By Step

You need to make sure that fresh air gets into your growing room. That’s because cannabis plants require oxygen too. And the air inside gets out. Just circulating the air inside won’t cut it.

If you want to block out the light, you have to make some sort of light trap vent that absorbs the light that comes in. But lets the air pass through. 

This can be easily achieved by installing square or round ducts. Let’s see how you can do that.

Method 1 of 2: Duct Installation

This is the easiest method to light proofing vents. Let’s see how it can be done.

Step 1 of 2: Paint The Ducts Black

Light can get reflected. Shiny painting or coating can let some light bounce around and pass through. 

So before installing the duct, make sure it’s black on both inside and outside. That ensures that it won’t even help reflect leaking light as well.

Here are our top picks for black paints you can choose.

Step 2 of 2: Make A U-Shape Bend Using a Duct

Take your duct and make a U-shaped bend with it. Because as we know, light only travels straight. The light coming through the vent will be lost inside the U bend.

Source: youtube

You can attach an exhaust fan on the outside of the vent or at the end of the duct. You might also use a filter of some sort. That will filter away unnecessary particles in the air. 

In case you’re looking for exhaust fans, here’re our top picks on that.

Ducts are very simple to DIY and they work great too. But there is one catch.

Method 2 of 2: Roof Panel Method

Hemp plants need 12 hours of light and 12 hours of darkness. In the light period, if you have ducts, you have to use extra vents to let in light. 

Because once the grow tent light traps are installed, you can not let light in. 

So if you want to make a controllable system, then you have to avoid the Duct method. This way, you can change to let light pass or not. Thus, introducing the roof panel method.

This can be done by using some rods, some spacers, and some roof panels. Let’s see how you can do that.

Step 1 of 4: Make A Wooden Frame To Attach To Your Vent

You’re going to make a flap system that can turn to let in or block light. And to install that outside your vent, you need to use a wooden frame.

Measure your vent size carefully. The height and length should be slightly bigger than the vent. And the width should be the same as the width of the flaps.

Step 2 of 4: Cut And Paint Roof Panels

Take any regular roof panels you can find at stores. It’s better if they are black. In that case, you can choose the Generic Polycarbonate roof panel. And if not you can paint them black anyway.

Then you mark them and cut them to the size that you want. If you can find the right size and use it smartly, you can get nearly 8 pieces out of one panel.

Step 3 of 4: Spacers And Rod Installation

You can use electrical conduits of your desired size to use as rods and spacers. PVC pipes will work too. 

Well, I hope that makes your shopping for a diy light trap for greenhouse a bit easier.

Then cut some of the pipes into equally small pieces to use as spacers. Or, you can simply choose the Metal Spacers Aluminum spacer.

Then make holes at the 4 ends of each cut-down panel. Make sure they all have the hole in the same places. Or they will not sit right when inserting the rod.

Step 4 of 4: Join All The Pieces Together

Lastly, insert the rod through the holes in the panels with spacers between each panel. And attach the rods to the wooden frame by drilling or screwing.

Now attach the final product to your vent. Now you can easily angle the panels to allow light in or block it off totally.

Well, that’s how you do it! The duct solution is a much easier way to get the job done. But if you don’t have extra ventilation to let in light, you have to use the roof panel method.

Things To Look Out For

As light is our primary problem, the light proofing has to be absolutely perfect. Because that ensures that your hemp is of good quality like Loud.

But as you are DIYing it, it won’t be perfect.

When you’re done, get into the room and make it completely dark. Thi is to check if there are any places that are leaking light.

Regular quality ducts most times have lots of holes in them. And they can let light pass. 

Just take the electrical tape, and cover any place that is leaking light. And that will get the job done for your diy light trap greenhouse or grow tent.


Does Sunlight Help The Growth Of THC In hemp?

Yes, studies have shown that increased intensity of sunlight can increase the amount of THC produced in hemp. There are specific colored lights that have a better effect. But in general, if your hemp plants are exposed to sunlight then they yield a better result.

How Much Time Does The Flowering Stage Last In hemp?

Flowering stage in hemp generally takes about 8 to 11 weeks. Different strains of hemp take different amounts of time for flowering. Such as Indica strains may take up to 10 weeks, whereas Sativa strains cake take nearly 12 weeks.

What’s The Ideal Humidity For Hemp Growing?

The ideal range of humidity for hemp growing is 40-50% humidity. Anything over 60 percent can harm your plants. It’s better to keep it under 40 percent when your plant is flowering. That will give you the best result from your plants.


You should now be able to make diy light proof vents for your greenhouse or grow tent. Just make sure your plants are getting all they need. And you’ll get a satisfying result.

See you soon!

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