Stevenson screen self build

[darc]

I am in the process of getting materials ready for the build of my Stevenson screen
I have been given some wooden louvre doors and am getting them ready to be cut to
size I have got many conflicting sizes and diagrams some are louvre both inside and outside others are just louvre on the outside and also were is the best place to get the instruments for inside the box, I would like it to be none digital as I have my vp2 for digital readings.
I have got also a small solar panel that will run a small pc fan if needed would just need to put a thermo switch on to it.

Any advice would be appreciated

[logjam]

I discovered that having louvres just on the outside reflected light, and heat into the box, especially at low sun altitudes. Louvres inside solved that problem without restricting the air flow. I found painting the inside matt black, and outside with enamel white gave the best results. I have tried using a fan, but it just introduced a hole in the box for heated air from the ground to get in. If you are going to use one, then perhaps placing it in some kind of pipe curved upwards and pointing north would be best. I am not convinced it helps in my location which gets plenty of air blowing anyway! I no longer bother with it.

[darc]

Hi thank you for the advice, I to am not convinced by the idea of a fan however on warm still days were the screen is going to be placed gets very warm with not much in the way of wind flow so not to sure as it would benefit the screen and if it does how much.

Geoff

[logjam]

Again from observation, the actual temperature on hot, still days seems to depend more on the surface underneath and around the screen. If the area is the usual grass, then it shouldn't heat up unduly, and the temperature inside the screen should be similar to the outside air anyway. More important will be how much direct heat finds its way into the screen. Good reflective white paint, and thick wood, and a secondary roof should take care of that.

[KevinF]

This was my effort Geoff

http://www.flickr.com/photos/78565286@N02/

It has been in use about a year now and because I already had the wood it cost very little, and with my limited woodworking skills I still managed.

Importantly, I have been very satisfied with my temperatures, with no silly records. The louvered ventilation grills were purchased from Screwfix for about £1.60 each.

Within the forum there are loads of threads that discuss homemade screens.

Hope this Helps

[darc]

Thanks for the pic's, They have really helped me make a decision on the base as I was not sure if I was going to have it on 4 legs or a single post like yours, after seeing how your looks
I think I will go down the same route as you have.

Thanks

[logjam]

Kevin, an excellent example. I also used a similar, if not the same make of grills. The only difference is that I included a second set of grills inside and painted them black for the reasons I mentioned above. Is there a reason for having the 'floor' slatted like that. I was unsure how to tackle that. Should air be encouraged through the floor or not?

[KevinF]

I tried to base my design as much as possible on an actual stevenson screen which does have ventilation below.

Certainly had I not had a screen the the WMR200 without would have recorded silly record temperatures. Lancashire does not have extremes. So I'm happy with what I've got. After a year the grill have a tinge of yellow - I'm not sure how to deal with that. I may just nip out and buy some more.

[darc]

You could just get a spray on plastic coat that should deal with the problem, I'm glad the
floor has come in to play i was just going to us half inch ply not sure now.

Geoff

[logjam]

The floor is an interesting point. Most illustrations of Stevenson screens don't show the floor so I just made one with thin, white PVC sheet. It would be easy enough to cut it into slats. My thinking was that I didn't want air rising vertically from the surface going into the box. I only wanted air coming in horizontally from the general environment.

The plastic on my grill tended to be slightly translucent and let in light and heat into the box. I applied thick enamel paint to outside of the the plastic grill. Painting the inside on the grills black stopped every bit of light and heat. Sunlight will affect the plastic pigment and turn it yellow, so I think a spray of white primer at least should be applied.

[darc]

Yes the floor is going to be a bit of a problem as in the pic's I'v seen don't show it very well
I was just going to use a piece of ply wood but don't no now as you say there could be a bit of upward heat reflecting from the floor and then into the screen.
I could do with more information as to floor design.

Geoff

[darc]

Well I have built the screen just a little bit more paint gone for a black interior
white outside and legs, I have got a half inch roof I will more than likely add
another roof leaving a half inch gap between them, floor is a single sheet of
ply, double louvre on all sides with a drop down door.
I will put some pic's on when Iv'e finished painting.

[darc]

Here are the pic's of my screen now up

[steve]

Nice job

But just one comment - you've apparently put the door facing south; it should be on the north side so the sun doesn't get in when you open it.

[darc]

Thanks Steve, I did not no that is that a really big no no the door is facing s/w, if it is it will not be hard to turn it round however I would need to chop down some bushes to get to the door.
just one other thing should I put a second roof on it leaving a gap between the 2.

Geoff