This is from memory, so bear with me. It was partly the flu epidemic and partly tuberculosis, for which the "cure" was to send you to a sanitarium in the Adirondacks, where you'd sit all day in a breezy sun room. Articles from the '20s touted the health benefits of a home sunroom, offering exposure to light and air. They became a tremendously popular feature in all house styles, from Spanish to Tudor to colonial. Photos suggest they were decorated to bring the outside in, with wicker furniture and lots of plants.

That help?

The idea of the conservatory was brought to many people's attention because of the 1851 Exposition in London; crystal palace. So glassed in rooms became highly desirable. Once machine-made millwork was able to be distributed by rail cross-country, and glass production also became mechanized, the cost was brought within the means of many more homeowners. Large expanses of glass begin showing up in house plans from A.J. Downing onward.
Sleeping porches were popularized by various hygienic concerns relating to both TB and T.R.
Casey

And the enabler: All that happy money floating around in the 20s boom, much of which went into the lovely homes still in demand today.

I don't think there's a single house with a sunroom that I pass without thinking, I would so love one of those.

Thank you all for the responses. I've been curious about this for a while and these answers make a lot of sense. The old sunrooms add so much character to those houses...and it is nice to have a sunny spot with wicker and plants :)

Our previous home, a 1916 Arts and Crafts, had not only a conservatory with windows on on 3 sides, but also a fountain right in the middle. The floor was beautiful black and white hex tiles, and it had fabulous beams, woodwork, and gorgeous french doors. Probably pretty upscale in its day. Above the conservatory, was another sunroom, not insulated, with single pane windows all around. It was probably used as a "sleeping porch" during hot summers before A/C. We eventually had it insulated and better windows installed. We used it as a bedroom for 2 of our granddaughters when they visited. All decorated in sunny yellow. They loved it.

Joyce- I don't suppose you have any pictures? :)

We love ours, even though it's small. Everybody wants to sit there on a sunny day.

Marcolo- Do you have any pictures?

Also, I would like to ask your opinion...I want to put an addition on the side of our farmhouse, but I want it to 'work' with the rest of the house. It would be to the left side (and behind) the sun porch. There are no windows planned for this side of the addition, but I'm wondering if lattice panels or something else, would tie in better...maybe make it look like a breezeway?

It's the south corner of the house, so it would be great for growing climbing roses and other vines. I also want it to look nice, since we can see it from one corner, of the sunroom. Thank you :)

I can't picture what you're describing. Do you mean an open porch?

Marcolo- Here's a rough sketch...each square is 2 feet. The living room, dining room, sun porch are there and I'd like to add the bedroom wing, but need it to look right, with the rest of the house. Do you think lattice panels would work? I don't have any windows on that wall, but there will be some on the side and back, of the bedroom wing.
{{!gwi}}From Snow White album

I guess I'm trying to 'disguise' this big wall and make it look like part of the garden...so here's one idea.

Lattice panels, with vines on them and maybe some statuary... {{!gwi}}From Snow White album

I wouldn't mind having the lattice on two sides, even if it made the sunroom just a bit shadier. I'd love to plant some climbing roses and if I made this front area, into a little courtyard...I'd finally have a place the deer wouldn't be able to get into :)

what will be in that space between the sunroom and the bdrm? anyway to open it up to an outdoor living space accessable from your bdrm?

Fallingwaters- I was thinking of a courtyard, that would be entered from the front. There are no doors or windows on that bedroom wall, which is why I was thinking about using the lattice panels. Also, our driveway and parking is on that side of the house. It would be nice to screen that off, a bit.
{{!gwi}}From Snow White album

While it's nice to have outdoor access from the bedroom, it wouldn't really work, in our space. If it's not screened or glassed in, chances are you'd find a racoon or porcupine, when you open the door :)

Your sunroom will get dark if there's a covered space beside it, which sort of defeats the purpose. A solid wall of lattice on its own would look odd, I think. You still need to see that as an exterior house wall. I'd prefer a nice, big trellis with roses or something trained on it.

You mean, a trellis off the sunroom...or the bedroom? I was thinking a courtyard space, not covered, with lattice on two sides...but I am completely open to suggestions! Thanks for the help :)

Where you plan on a lattice, I would simply do a large trellis. I think a lattice covering an entire wall would look odd, and probably not be very good for your siding or shingles.

lavender - what is the exposure on that side of the house. N S E or W. This will greatly affect what plantings will thrive and how much sun you will get in your sunroom. What siding are you using, Cedar Shakes, painted clapboard? You will need air flow between lattice and siding. New dawn pale pink roses would be beautiful but again it goes back to the exposure. ;)

CJC- The bedroom wall and the short side of the sun porch, face southeast. The long wall of the sun porch faces southwest. It's a nice, sunny corner :)

Marcolo- Do you mean something like this? That would work better, for roses...and I see what you mean about the lattice panels, not looking as good. {{!gwi}}From Lavender's Garden

Great for roses! Take a section of brass pipe or L brackets to hold the trellis off the house. You can then unscrew the brackets if you need to paint the house. I don't know where you live but New Dawn Roses, Zephrine Drouhin (David Austin)no thorns are two beautiful fast growing trellis roses. Hydrangea planted in front of them or pink Fairy Rose shrub roses would be beautiful. Another idea is climbing hydrangea. You could grow morning glories up with the roses too. The trellis above would be great!This will be a beautiful area!

Cjc- That sounds beautiful, but Zephirine Drouhins do not like my place...too much humidity with our creek, but they love it, up at my mom's. They're fragrance is wonderful.

We're in zone 4, but I'd love to find some nice climbing roses! New Dawn is a possibility, but I've been thinking about a John Davis rose...they're hardy to zone 2 or 3 and they bloom all summer. {{!gwi}}From Lavender's Garden

The fairy roses are a great idea. I already have two and might buy a few more. Our frost free season is pretty short for morning glories, but clematis do very well. Thanks for the encouragement...I think it would be a pretty little courtyard area, too :)

I live in a neighborhood with lots of 1920s houses, and I don't see any more sunrooms in them than in newer homes. Maybe it's a regional thing.

What I do see much more in pre-1950 houses are large screen porches, often in the front, some of which have since been converted into sunrooms. The screen porches were popular because air conditioning was still expensive and rare, and the big open screened rooms allowed for a good breeze and kept you in the shade to stay cool. Once A/C became common, the screen porches all but disappeared on new houses, and those already there in older homes often got converted into enclosed rooms.

Actually, the most common houses to have sunrooms around here are late-90s-to-early-2000s McMansions.

We added on a screened in porch to the rear of our house as part of the reno. It has glass windows that can be put in for the cold months, so some call it a Florida room. I wanted an old style outdoor space that lives like an indoor space and where we won't get bitten by mosquitoes. Before adding it on, we never ate on our porch because of not wanting to be chewed up. We used the porch only for big bbqs with lots of citronella candles and bug spray.
We intend to decorate it to be like a sun porch. We love how we can leave our back door open and don't have any screens on our back windows because the room works as our screens. With the ceiling fans in our house and in the porch, it really lets us have natural air & breezes instead of refrigerated a/c all summer.
Several people have seen it and mentioned turning it into another indoor room, but with the den adjacent, we have no use for more indoor space. It is meant to be a place we can be outdoors even if it rains or is hot in the sun as it provides shade from the midday heat. I can't wait to have it set up with comfy seating so I can enjoy a cup of coffee out there while working online or just plain old surfing for fun.

LL, I'm near the other Washington, as in D.C. (I think you were referring to the state). We really get the four seasons here in the extreme - blistery icy, windy and cold for 2-3 months in the winter, humid 90-100F days in the summer.

I see alot of screened porches on pre-WWII houses even in the cooler northeast.

No, actually front porches typically pre-date the '20s--the exceptions tended to be people using old, 1910-era bungalow or Mission house plans. Once cars got on the roads, builders started putting outdoor space on the sides of houses to get away from the dust, smoke and noise. Given that the 1920s was the heyday of national house plans that were used from CA to Boise to Chicago to Boston, and overwhelming numbers of those plans show sunrooms of some sort, I'd say a 1920s neighborhood without any sunrooms at all would be of interest to architectural historians. That would be the unique regional distinction.

Lee- Out here, Washington is ALWAYS the state...you would be in DC or Washington DC. It's funny that back east, people refer to us as 'the state' :)