Existing passive solar room gets too hot year-round

Hi! I'm new to this forum and I need some advice on an existing passive solar addition on the back of the house I recently purchased in Northern New Mexico. It was built as a "passive solar greenhouse" but seems to get too hot for plants to grow even in the winter. I'd love to use it year round both as a sunroom of sorts and to grow a few veggies that my toddler could help me harvest to learn about how things grow, but nothing too officially "greenhouse" about how I'd like to use it 😅. Whrn I was younger, I used to be really into the idea of passive solar and permaculture, etc. and was excited to see that the house had this solar room when I bought it, but now I feel like I'm in over my head. The windows are massive (7+ ft tall), slant back into the room a bit, and the shades they had when I bought the house are too badly damaged to salvage. I'm wondering if there's anything I can do in terms of purchasing new shades, maybe adding awnings or trees, etc. to make it more possible to use this room for actually living in? I'm going to try to attach interior/exterior photos of the room as well as an overhead view that shows its orientation. Also, I'm a single mom whose primary source of income is teaching public school, so I'm looking for the most cost-effective solution(s) possible. Thanks in advance for your help! 🙂

Oh, and pardon the mess in the photos-- house was a foreclosure that needed extensive renovation and since thus room isn't currently usable it became a catch-all for construction materials 🙃.

Welcome to the forum!

Do any of those windows open?

If not then the person who built the structure did not understand how passive solar works.

My suggestion would be to figure out a way to add some vents.

If it were mine, I would make lightweight screens to cover the windows.  You could very easily make frames from 1"x1" lumber, cover them with shade cloth, and attach one to each individual window.  I would probably use magnets to attach them.  If you want more heat to come in, you could remove the covers from one or more of the windows in the winter or on cooler days.

The windows on the ends appear to open.  With both of them open, you should be able to get a cross breeze going through that room.  If that isn't enough to ventilate it, one small solar panel with an attached fan would definitely pull air through.  If that is needed, I would cut out a piece of thin plywood the proper size to cover the window and then cut a hole in it the size of the fan.  If the area around the fan is open, it won't pull air through, so you need to cover all parts of the window that the fan isn't covering.  I would put the fan as high up as possible in the window.  If you wanted to improve on that idea even more, you could run a duct from the fan up to the ceiling.  That would pull the warmest air in the room out the window and pull cooler air in from the other window.

Welcome to Permies!

I second the idea of ventilation. That is probably the most cost effective way to help. Shade cloth is good, but if you are not careful, you can end up with expensive options.

I generally have the opposite problem, as I live in a fairly cool climate, but I wonder if adding some water barrels would help soak up some heat during the day, and release enough of it at night?

Thermostatic exhaust fan in that top corner as high as you can get it without getting into the framing. It will turn on whenever needed even while you’re at work.

IKEA sells shades that double stick tape to the windows so they will work with the negative slope of those windows.

It's good that the floor is stone - that will help soak up the heat and re-radiate it. If I were putting shades up, then I would consider shading the outside of the windows - more of an overhang will help stop at least the summer sun getting into the room as seen in this image:

(source)

passive solar design

That will help keep the room cooler in summer at least. It looks like there is not much to fix to above the window, so a stand alone awning, or maybe a pergola with a plant climbing up it, might be better. I've tried to sketch something up...I think Leigh had a similar problem with her greenhouse house extension - that had a glass roof too (but some opening windows), so you have an advantage there.

It's a lovely room though, so I hope you can make it useable!

I'd check for a local to you Habitat for humanity ReStores, or local recycle resell type store. Perhaps you can score a set of blinds. as for a longer term fix i would consider extending the roof line out a bit more to shade the summer sun, while letting the lower angle winter sun in. In the mean time do you have a set of white bed sheets you could pin in place??       John

Thanks for the suggestions so far! It sounds like ventilation appears to be a big part of the potential solution as well as figuring out a better way to shade the windows. There was an automatic exhaust fan in one corner of the room, but it vented into my daughter's bedroom, which was a no-go, especially in the summer, so I removed it. However, I could probably have a hole made in the exterior wall adjacent to it and re-install the fan. There's also a door in that wall that leads to a shaded patio that I could potentially use as an important part of cross-ventilating the room. I'm attaching a photo that shows door and fan on the back wall of the room.

Over heating during the winter seems like an amazing resource.
What kind of HVAC system does the house have?
Does the house have a basement or crawl space?
Venting the sun space into the return air of a forced air furnace or into space under the the house could defer heating costs.
Pulling cooling air from the space under the house might be detrimental or it might be fine.

A heat pump water heater could cool the space.
Plumbing it to another water heater  and a hydronic heating system in the living space would allow you to transport that heat to where it's needed.

Not sure how ro reply to a reply here, but in response to William Bronson's reply-- both of those are possibilities, actually. The crawl space access is actually in this solar room (under the green tarp in the lower right-hand corner of the last photo) and the heat return will soon have a 2nd intake just through the door from the solar room if we decide to add central AC or swamp cooling to the house (still trying to decide).

Adding a couple more photos to show where the old fan was (going to ask my handyman how hard it would be to move it to the adjacent wall, whether it would need rewiring, etc...as you can see it's still just hanging there since I couldn't decide what to do with it. I only knew I needed to patch the hole in my daughter's wall so her room could be used immediately). The door from this room into the house is the old back door to the house which leads to a central hallway, so the extra heat from the solar room really is helpful for heating the house and cutting down on winter heating bills. It's too hot in the room itself to use it as a room, though, which is what I'd like to remedy. I kinda get why the previous owners added the fan, as it vents more heat into another part of the house, but they weren't using my daughter's bedroom as a bedroom and I need to use it as one.

For relief during the summer , how about awnings?
They are adjustable and removable and not hard to diy.

Hello!
A simple trick from my friend's grandpa's greenhouses: paint the window panes. You can use soap suds or potato/cornstarch in water, make a thickish solution, and just paint the windows with a big brush. You can make big sweeping curves with a broad paintbrush or try to keep it even with a roller, or spray it on... The "paint" is biodegradable and will wash off in the rains/erode in the winds. You can choose which bits of the windows to cover, e.g. leave a strip at head height so you have a view, paint every other window pane, paint it in stripes so there's still direct sunlight coming in but not all over all the time.
I face a similar issue in Old Mexico, where the skylight allows natural light into the living room - but it turns out that sun is too harsh for the plants we keep there, so they face an all or nothing situation where it's either laser-burning sun, or shade. The light's gorgeous though.
NB I haven't implemented the potato-starch paint solution yet, but let me know if you do it, then I'll join you and we can compare notes!

All good suggestions/
I would design an outside eave that will control seasonal sun access.
It is a straightforward system.

If you need quick and cheap, see if you can salvage material to build a trellis about a foot or two away from the windows and grow a heat-loving runner bean up them. Some bean seeds can even be bought in the bulk food zone of your grocery store.

I did similar years ago when I needed instant privacy in a new housing development. It did a great job, Scarlet Runner bean flowers are pretty, and the beans are yummy.

Bevin Carnes wrote:Not sure how ro reply to a reply here, but in response to William Bronson's reply-- both of those are possibilities, actually. The crawl space access is actually in this solar room (under the green tarp in the lower right-hand corner of the last photo) and the heat return will soon have a 2nd intake just through the door from the solar room if we decide to add central AC or swamp cooling to the house (still trying to decide).

I recommend the swamp cooler!  A fraction the cost to run.  Here in western colorado, and many other places, there are issues with running the air conditioning in the summer afternoons… just when you need it!  The power companies where I have lived “ask” for “permission “ to control people’s air conditioning at their convenience.  They cycle on and off hoping to keep everybody “cooler”, without grid failure…. The air conditioner and heat pumps require a compressor.

A swamp cooler just runs a fan and a water pump.

New Mexico is arid enough for seamp coolers.  Just remember, pull outside air into the swamp cooler, and open strategic windows to allow air out.

I agree with all these great suggestions.

I want to emphasize the idea of water barrels to absorb heat.

And I suggest getting cool night air in, it will carry the excess day’s heat out.  If the current windows aren’t big enough, then night time cooling would be as high a priority as searching for the means to transfer the excess heat into your house.  

Hi Bevan, I had a similar problem with my passive solar house in NZ. I made curtains lined with metallic shade cloth, they work really well and create a lovely soft light. I see your window is on a slope so I guess you'd need a way to attach the mesh to the bottom frame... maybe sticky velcro dots for when it's in use. Here's a link for the mesh I used. https://wintergardenz.co.nz/shadecloth/alishade-silver-reflective-shademesh-4mx5m/

Have a look at this product, I used it on a skylight with great results.
https://ecomasterstore.com.au/products/renshade-reflective-rolls-for-hot-pergolas?srsltid=AfmBOooUyz1i5VAISIVF3q97cmF5jRLimEYkS6ID1yhglJ7BnPjWX9oL