Air Conditioning Load on Glassed in Lanai
 

We recently had our ~300 sq ft. south-facing lanai enclosed with single pain / non-insulated glass on our ~1900 sq ft home. The wife wants "open living" (i.e. to keep the doors to the lanai open) and thought we could do it after we blew insultation into the lanai.

I'm concerned that not only are the new windows and door not double-paned (i.e. no insultation) but also the added space will strain our AC unit In fact, when I saw the price of a mini-split I figured we might be able to extend the existing ductwork into the lanai after insulating, but I was told from multiple contractors that this would strain the AC and is not to code.

Questions: even if we blew insultation, how much cool air would we be bleeding from the single-pain glass? With this leakage and new 300 sq feet to cool, how much of a load/strain would leaving the doors to the lanai open place on our AC unit and is that comparable to having the ducts directly into it?

My idea of "open living" is not keeping the doors open, but rather using the lanai occasionally with the doors open (i.e. air conditioning from the home) but mostly using it later at night with windows open for a breeze to naturally cool it, but I supposed we're going to have to minimally both blow insulation and get a mini-split if my wife wants to keep the doors open all the time, correct?

You definitely need to add insulation to the ceiling, as much as possible. Attaching ductwork to the existing HVAC system is not a good idea, and it most likely would violate the building code. Some contractors won't even do it. Adding a mini-split system is a good option but, I would first try leaving the doors open to the lanai and see how comfortable it makes the lanai. If you don't have a ceiling fan in the lanai, you should install one to circulate the conditioned air. If the lanai is mostly glass, single pane was not a good idea. You may also encounter condensation on the inside of the glass in the winter. A rule of thumb is that, in a typical house, you lose about two-thirds of energy through the roof, and about one-third through the windows. If the lanai is mostly single pane glass, you are losing even more energy through the windows.

I cannot answer your question, but I can provide some advice. We also enclosed our lanai, and went to add AC. I ended up contacting an Engineering company to produce a ~20 page report for the county at a cost of $250. The report gave me the exact size of the AC required, however, I came up with the exact same number when i was researching mini-split systems, several of the sites have a way to fill in the room info to get the size requirements. As to whether this will strain your existing system I have no idea. I am going to send you a PM also.

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Good suggestion. But make sure it is large enough. I would be thinking of at least 12,000 BTU and one that heat and cools for a lanai that has single pane glass windows. I don't trust the square footage capacity touted by the companies that make them.

I thought that because those are portable single units and exhaust out a window they would be prohibited by the deed restrictions. No? My deed says that only central and split unit A/C is permitted.

I took that to mean no portable units. But maybe my interpretation is wrong.

Not that that matters, as it would be inconspicuous.

Window unit air conditioners are prohibited. It is stated in the deed restrictions document. But I called the Community Standards office and asked them if the type that has a round exhaust duct through the window is allowed and they told me that they are allowed.

Durning COVID our HVAC died. Chuck did his best but finally had to put it out of misery. It was August 20, outside temps 87-98 HVAC back ordered 5 weeks.

Week 2 The crew brought a 10,000btu portable for our bedroom, vented through window with a special kit.
Bedroom was 14x18, closing both doors running 24/7. Inside temp of house around 84 at night. Bedroom temp 79

Some nights it was cooler sleeping in the screened lanai with a breeze, than the portable ac in the bedroom. Running portable AC for 3 weeks 1 day, Our Seco billing was $161 more than our July bill with a functioning AC. Bedroom faced south east. It was a long 5 weeks

We enclosed our lanai years ago and when we did, we were told if we added AC or Heat it would be considered another room, increasing the tax.
I don't know how your house is structured, but our lanai was built under our roof line, so it was already insulted, plus there was already a fan in place.
Now our lanai faces west, and we have two sets of sliding doors the one we added to enclose the lanai and the one that came with the house leading to the lanai.
When we are not using the space, the double doors add insulation and when we are going to use the space, we just open the sliding doors to the house, and the lanai temperature with the fan quickly becomes the same as the rest of the house.

What you said in your second sentence is not at all typical. The builder does not install insulation above the ceiling in either the lanai or the garage because these are unconditioned spaces. Most likely, there is no insulation above your lanai ceiling.

We glasses in our lanai, 400 sq ft. BUT IT faces north
The sliding door is open all the time. 2 ceiling fans, we tried the stand alone air for a while and finally put in a split, the problem with it is it drips if we try to get it to cool to match. We also put in the honeycomb shades which do help. Good luck.

It sounds like your condensate drain is clogged or somehow not working properly. You may have a condensate pump that is broken, or the condensate pipe is leaking.

We expanded our lanai from 180 to 320 sqft. Enclosed the lanai and added a 12K BTU mini split. The AC in the house died at the hottest time of the summer. If it weren't for the min-split, we would have moved to a hotel. With a couple of fans, it supported cooling the central area of the house. The contractor added one of the stand-alone AC units for our bedroom, and we survived the 5-week period to get the AC fixed. If it weren't for the mini split, we would have been in dire straits. Having the completely separate AC unit was a godsend.

Somewhat unrelated, but 5 weeks for 2 of you to get AC fixed?!!! I hope you looked around for better service. If so, then that timespan is really unsettling. There's always something that can be fixed via readily available parts. Maybe you were convinced by them you had to replace the whole system. Mine has been completely refurbished, one part at a time as they failed.

My glassed in lanai is open to the house and has AC running to it. Even with double paned windows, I usually have to run a fan to feel cool in there. If you want to avoid various extra costs, I would just have fans to cool you off in there and keep it closed off to the house if your wife can stand it!

Do yourself a favor. Insulate and put in the mini-split you won't regret it. We've tried all the other options, 1. leave the slider open, place a fan in the doorway (still too hot) 2. portable ac (still too hot).

Mini-split, roll down shades and insulation is the way to go. We used Sun Kool, but Munn's is a good option as well.