Three words used interchangeably in listings, and they describe three different buildings with three different purposes. 🏛️ If you are shopping and finding the results confusing, this is usually why. A greenhouse is for plants, a sunroom is part of your house, and a conservatory sits between the two.
Getting the category right matters because it determines the budget, the permitting path and whether you end up with the building you were actually picturing. 🧭
🌱 Greenhouse
A detached structure, glazed on all sides including the roof, designed to grow plants. Everything about it serves that: maximum light from every angle, vents that open, a floor that can be soil or gravel, and a tolerance for humidity that would ruin a domestic room.
- 🔆 Glazing: single glass or twin-wall polycarbonate, prioritizing light over insulation.
- 🌬️ Ventilation: roof vents and louvers, sized generously, because overheating is the main daily risk.
- 🧱 Foundation: gravel, pavers or a slab. Frequently no floor at all in the growing area.
- 🌡️ Comfort: not a design goal. It is hot in the afternoon and cold at night, and the plants do not mind.
- 📜 Permitting: a detached accessory structure, subject to size thresholds and setbacks.
Modern glass greenhouses blur this a little, because a large glazed structure with a paved floor genuinely can hold a table and chairs. But the building is still designed around light and ventilation first. 🪑
🏡 Sunroom
An addition to the house, with a solid insulated roof and glazed walls, built as habitable space. It is a room of your home that happens to have a lot of windows.
- 🧊 Glazing: double or triple glazed units, prioritizing insulation over light.
- 🏠 Roof: solid and insulated, often continuing the house roofline.
- 🔥 Climate: heated and often cooled, integrated into the home's systems.
- 🧱 Foundation: a full footing to residential standards, tied into the house.
- 📜 Permitting: a residential addition. Full building permit, structural review, energy code compliance, inspections.
⚠️ The cost consequence is large. A sunroom is priced and permitted like an addition, typically several times a greenhouse of similar footprint, and it takes months rather than weeks. Plants can live in one, but the environment suits furniture and people, not tomatoes. 💰
🏛️ Conservatory
A glazed structure, including a glazed roof, attached to the house and intended as living space. The historical form is the Victorian orangery, and it genuinely sits between the two others.
- 🔆 Glazing: walls and roof, often double glazed.
- 🌡️ Climate: the honest weak point. A glass roof loses heat in winter and gains it enormously in summer. Without shades, shading and ventilation, a conservatory is genuinely unusable for part of the year.
- 🧱 Foundation: full footing, as it attaches to the dwelling.
- 📜 Permitting: attached, so usually treated as an addition rather than an accessory structure, with the fuller review that implies.
The thing conservatories offer that nothing else does is the sky. A glass roof changes a room in a way no amount of windows replicates, and that is what people are buying. The trade is that it needs active shading and ventilation to be comfortable. ☀️
⚖️ Where they genuinely differ
- 🏗️ Attached or detached. A greenhouse stands alone, the other two join the house. This single fact drives most of the permitting and cost difference.
- 🏠 Roof. Glazed on a greenhouse and a conservatory, solid on a sunroom. This is the fastest way to tell a sunroom from a conservatory in a photograph.
- 🌡️ Insulation priority. Greenhouses trade insulation for light. Sunrooms do the reverse. Conservatories try to have both and compromise on each.
- 💰 Cost order. Greenhouse, then conservatory, then sunroom, and the gaps are large rather than incremental.
- ⏳ Timeline. A greenhouse is a lead time plus a two to three day build. The other two are construction projects measured in months.
🧭 Which one do you actually want?
- 🍅 "I want to grow things." Greenhouse. The other two are poor growing environments and cost several times as much.
- 🛋️ "I want another room in my house, year round, comfortable." Sunroom. Budget and permit it as an addition.
- 🌟 "I want to sit under glass and see the sky." Conservatory, with shading and ventilation planned in from the start rather than added after the first July.
- 🪑 "I want somewhere beautiful to sit among plants, but I do not want a house addition." This is the case people most often get wrong, and the answer is usually a glass greenhouse, dimensioned as a room rather than around bench runs.
That last one deserves expanding, because it is the most common mismatch we see. Someone pictures a conservatory, prices one, and abandons the idea. A detached glass structure delivers a large part of the same experience, glazed roof included, at a fraction of the cost and with a far simpler permitting path, because it is an accessory structure rather than an addition. 🏛️
Models like The Manor exist precisely for that use: glazed on all sides and overhead, dimensioned around furniture rather than bench runs. The trade is honest, though: it is not insulated to residential standards and it will not be a comfortable room in January without heating. ❄️
📜 The permitting gap, stated plainly
This is the difference with the largest practical consequences. 🏛️
- 🌿 Detached greenhouse: often exempt from a building permit below a size threshold, though setbacks, lot coverage and HOA rules still apply. Frequently a matter of one phone call.
- 🏠 Attached conservatory or sunroom: a residential addition. Full permit, structural and energy code review, inspections, and a timeline measured in months.
Even a lean-to greenhouse against the house can cross this line, since attaching to the dwelling frequently reclassifies it. We went through the thresholds and the questions to ask in our permits guide. 📞
🌿 Can you grow plants in a sunroom or conservatory?
Some, and it is worth being realistic about which. 🪴
- ✅ Works well: houseplants, citrus in pots, a fig or an olive, herbs on a sill, overwintering tender specimens.
- ⚠️ Works poorly: seedlings, which stretch toward the light in a room glazed on fewer sides, and anything wanting high humidity.
- ❌ Does not work: productive vegetable growing. The humidity a tomato crop generates is actively bad for a room with furniture, drywall and upholstery.
The humidity point is the one people discover late. A serious growing space wants to be damp; a habitable room does not. That conflict is fundamental and it is the real reason the two building types stayed separate. 💧
❓ FAQ: greenhouse, sunroom and conservatory
What is the difference between a conservatory and a sunroom?
The roof. A conservatory has a glazed roof, a sunroom has a solid insulated one. That single difference drives the light, the comfort and most of the cost. 🏠
Is a greenhouse cheaper than a conservatory?
Substantially, and the gap is larger than most people expect. A detached greenhouse is an accessory structure with a simple base; a conservatory is a house addition with a full footing and a full permit. 💰
Can I use a glass greenhouse as a garden room?
Yes, and that is exactly what the larger glass models are designed for. Plan for a paved or slab floor, shading for summer and generous ventilation, and accept that it will not be a January room without heating. 🪑
Do conservatories get too hot?
Without shading and ventilation, yes, reliably. A glazed roof takes the full midday sun. Shades, roof vents and cross ventilation are not optional extras on a conservatory, they are part of the design. ☀️
Which adds most value to a house?
A well-built sunroom, since it adds permitted habitable square footage. A conservatory adds less and a greenhouse adds least, though a handsome greenhouse is a genuine selling point in the right market. 🏡
Can I attach a greenhouse to my house?
Yes, that is what a lean-to model is, and it borrows warmth from the wall. Be aware that attaching to the dwelling often shifts it into addition territory for permitting purposes, so check before ordering. 🏗️
🧭 The short way to decide
Ask what the space is for. Plants, and it is a greenhouse. People all year, and it is a sunroom. People under an open sky, and it is a conservatory. 🎯
And if the honest answer is "plants, but I want it to be beautiful and I want to sit in it", that is a glass greenhouse sized as a room, which is the option that gets overlooked because it falls between the three words people search for.
The Prime Greenhouses range covers both ends of that, from polycarbonate growing structures to glazed models dimensioned around furniture, with footprint and ridge height published on every page. Working out which footprint suits the way you intend to use it is the next question, and we took it apart in our sizing guide. 📐