Recently moved into a new house that has nothing blocking sunlight from the West - no trees, no back neighbors, etc. The master bedroom is a particularly big recipient of this constant afternoon sunlight as it sticks out to the west and has giant windows facing west that take direct sunlight from about 1230pm to 830pm every day right now. About 60% of the west wall is the large windows.

The windows have shudder shades on them that I keep shut and very dark drapes. It blocks virtually all the sunlight in true blackout fashion. However the room is still extremely hot (cannot get it below 78 until well after 9pm). Per HVAC repairman, HVAC is supposedly operating fine. So I have been thinking it is simply the orientation of the windows along with 100+ degree heat and no shade whatsoever just beaming into these windows every day.

I put a Bluetooth thermometer between the shades and the glass and was shocked to see during the hottest points it would get to over 120 degrees in between that space - was expecting more like 90ish. My assumption is that despite the shades and the drapes, some of this extremely hot air is leaking out and killing any chance the HVAC has to actually cool the room while the sun is heating up that air. The ceilings are fairly high in the bedroom and the vents are in the ceiling so my guess is that the hot air kills the A/C air before it even starts the journey down. I am looking at getting some solar shades installed on the outside of these windows and if my assumption is correct, I suppose that should help big time with my issue.

My question would be whether I am way off base in this thinking or if the shudder shades and the drapes should be enough to keep the sunlight/heat out despite how incredibly hot it actually gets near the windows? If they should be enough then perhaps the solar shield is a waste and I should push further on the HVAC efficiency.

Also any thoughts on the 120+ degree temperature? These are double paned windows that are about 15 years old and they have a slight tint on them. If I open the shades the air gets down to mid-90's but this of course makes the room sun filled and even harder to cool down.

This company has been recommended on TexAgs before: https://lonestarsolarscreens.com/ and planning to get a quote from them.

Go heavier on the tinting. I DIY tinted my west facing window earlier this summer with a roll off of Amazon. I did not run a before and after test, but the temperature difference is palpable. Others have mentioned hiring a pro to do it (it was not the easiest DIY, but I old had one 3'x4' window).

What I purchased: https://a.co/d/7I25X5X

Discussion of Fabian, the go-to expert on auto and home tinting in Houston: https://texags.com/forums/46/topics/3384421/replies/65115740

The backside of my home is west facing as well so I ended up building my own solar sun screens with everything purchased at Home Depot. They make a really big difference in keeping the heat out, however, they really darken the room(s) quite a bit as well so I only put them up for 4 to 5 months out of the year during the summer months and remove them otherwise.

I had a professional install ceramic tint on my West side of the house. It made a huge difference. Before I could walk by the window and feel the heat coming through. Now it feels cool like the rest of the room. We have no window coverings inside or screens outside now.

1. Good idea! You can first experiment with a roll of solar screens, DIY stapled/taped to windows' exterior, THEN get a pro to do something $$$ permanent later if happy with your DIY results.
2. Heavy drapes/etc. certainly the same solution to heavy winters up North that works ... if blackout doesn't bother one of you, A-OK. 120F is to be expected West side & certainly if alum.frames.
3. Both the exterior HVAC and West wall need SHADE. Something built/bought for immediate (even a cheap tarp), something that would grow for later. Even a lattice that begins to grow evergreen vines could be a 3rd choice ... if this wasn't so severe.
4. You'll read on this forum's HVAC questions, reports that some like it hang-meat-cold when sleeping in MBR so install a window AC (e.g. a LG 10,000BTU) or mini-split to serve. Also a solution to glass rooms when heating up or for hot people's rooms so the rest of people in house don't shiver.
5. Still not working? More attic insulation over that room. Still no good? Ideas about wall insulation upon demand but you won't like them ..... Many will sugest this idea should be placed higher up in this list BUT we are still blind to what you have ....

Does a window unit generally use much electricity when used just at night time for sleeping?

ComeAndTakeIt said:

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I had a professional install ceramic tint on my West side of the house. It made a huge difference. Before I could walk by the window and feel the heat coming through. Now it feels cool like the rest of the room. We have no window coverings inside or screens outside now.

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this is what i would do as well

The LG 10,000BTU window unit has energy savings beyond the vast savings of leaving the whole house HVAC alone (set at higher than sleeping temperatures for some).
So we being with comparing 5/6 tons operating on-off while sleeping to 3-4-5 tons on-off (granted, perhaps less often cycles & some have variable stages).
Indeed 110v small AC will not be as efficient as 220v on energy bills.
Remember we are cooling down ONE room, not ALL.

All that said, can report NO energy increases when
LG 10k is employed nightly MBR/MBa
LG 10k is employed in glass studio when picking up dawn solar heat - rarely done
Trane variable HP thermostat set at 80F for house remainder (as she prefers)

Finally LG 10k specs
820 watts 7.7amps 110-115v
12.1 SEER
and can run issue free on a GFCI outlet that isn't overloaded by others