Sunrooms: an Alternative to Full Room Additions

Oak sunroom with ivy
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If you are seeking to add space to your home, one option is to hire a contractor to build a room addition that adds a bump-out or extension to the main footprint of the house. But it is also an option that can quickly alarm budget-conscious homeowners when the bids from general contractors come in. It is not at all uncommon for a custom-built addition to cost in excess of $100,000, and it is nearly impossible to get any custom addition of this type done for less than $50,000. 

These prices quickly cause many people to look for alternatives to custom room additions. One very popular alternative is a sunroom—a space that bridges indoor and outdoor spaces with a comfortable supplemental living area. Fact that a sunroom usually costs about half of a traditional stick-built addition makes this a very attractive option for many people. 


To the novice, the various terms used for add-on living space can be confusing:

Stick-built addition: Stick-built is the short-hand term for any kind of structure that is built from scratch. In this case, we are referring to house additions, room additions, and other bump-outs that are constructed from wood, concrete, glass, house sheathing, shingles—nearly every component that is used when building a home. These additions may have full basements beneath them in regions where that is the norm. A true room addition must have full electrical service and must also have HVAC service. This type of room addition adds to the official square footage of the house. According to the International Energy Conservation Code (IECC), any conditioned living space cannot have more than 40 percent of the wall space given over to glass windows.  

Sunrooms: The term sunroom is usually defined as a recreational space bridging indoor and outdoor living areas, usually with a considerable amount of wall space dedicated to glass—often as much as 80 percent. Building codes generally do not require a sunroom to have electricity or central heating/cooling service, although this is not a hard-and-fast rule: many sunrooms now have electrical services, and they may have supplemental heating and cooling. Sunrooms often are built on floating concrete slabs with shallow perimeter foundations, somewhat like those used for a garage; full basements beneath sunrooms are rare. 

Pre-Fab vs. Custom-Built Sunrooms

Within the sunroom category, though there are two subcategories. Sunrooms can be custom-built by a local general contractor who will design and build the sunroom to your specifications. Such sunrooms have traditional stud-and-truss framing and shingle roofs, but the walls are predominantly glass, formed by patio doors or full-length windows. More commonly, though, today's sunrooms are constructed from prefabricated kits that come with framework pieces of steel, aluminum or fiberglass, along with the glass panels for the walls. Pre-fab sunroom additions are assembled in puzzle-like fashion, usually by qualified technicians. The fact that these are "kits" does not mean that assembly is an easy DIY project, although many homeowners have successfully assembled them. A pre-fab sunroom is designed and fabricated off-site, then is shipped in pieces to your home packed in flat cartons. Assembly can be done by a homeowner, or more often by a contractor affiliated with the kit manufacturer. 

Costs of Sunrooms

Costs for sunrooms vary enormously. A recent survey showed that the average cost of a sunroom was $15,104, nationally, but that costs in excess of $75,000 are also possible for a large sunroom square feet) when a new slab-on-grade foundation was required. 

Here are some typical costs for a 15 x 15-ft. sunroom kit:

  1. Starting price for wooden kit sunrooms built with standard materials is about $15,000.
  2. Top-of-the-line aluminum and glass kit sunrooms can cost as much as $22,000. 
  3. Expect to pay $20,000 to $35,000 if you want the sunroom to be a four-season space, with finished walls and wiring and heating service. 

Components of a Sunroom

Since sunroom builders in recent years have been stepping up their game and rewriting some of the rules, these distinctions between stick-built additions and sunrooms are constantly changing and narrowing. For example, there was a time when most pre-fab sunrooms were not wired for electricity. Now, this is a viable option with most sunroom packages.

  • HVAC: Sunrooms are not required to have central heating and cooling (HVAC). Custom-built sunrooms usually have at least heating, often in the form of electric baseboards or fan-driven heaters. True room additions, on the other hand, must have the same central HVAC service as the rest of the house. 
  • Electrical service: Sunrooms are not required to be wired for electricity, though they increasingly are, especially when they are custom built. Even pre-fab sunroom kits may have provisions for adding electrical service. Stick-built room additions, on the other hand, are required to follow the same code requirements for electrical service as the rest of the house—which is one of the reasons they are more expensive than sunrooms. 
  • Construction costs: On the whole, sunrooms have a lower construction cost per square foot than do regular room additions built by general contractors and subcontractors. Square footage costs for sunrooms is usually about half that of room additions.
  • Provides supplemental space. The main purpose of a sunroom is to provide supplemental space with generous natural light for reading, growing plants, housing a spa, etc. This is an important real estate distinction because supplemental space is viewed differently from the essential living space that is provided by a true room addition. In short, a true room addition adds more equity value to your home than does a supplemental sunroom.

    Misconceptions About Sunrooms

    In their eagerness to add a sunroom, homeowners often make certain mistaken assumptions about sunrooms. Here are some corrections to common misconceptions: 

    • Sunroom DO REQUIRE building permits. In most communities, even the smallest sunroom, kit or custom built, will require a building permit in order to construct it.
    • Pre-fab sunrooms are not always cheaper than custom-built sunrooms. There are many different add-ons you can specify for a pre-fab kit, and a top-of-the-line sunroom kit with all possible options can approach the cost of a room addition. 
    • Your sunrooms may need a foundation. Foundation requirements are as varied as the localities where these codes apply. Generally, you will need a proper building foundation for your site-built sunroom, although pre-fab sunroom kits can sometimes be assembled onto existing patio slabs or decks. 

    Pre-fab Sunroom Companies

    Some reputable pre-fab sunroom manufacturers include: 

    • TEMO Sunrooms: Beginning in 1967 with founder Nino Vitale, TEMO has been making sunrooms, screen rooms, and patio covers ever since. Now located in Clinton Township, Michigan, TEMO has expanded to basements/additions and pergolas. TEMO sunrooms are installed in 1 to 2 days.
    • Patio Enclosures: Based in Macedonia, OH, Patio Enclosures has been making sunrooms since 1966. In addition, the company makes solariums, screen rooms, sunroom blinds and shades, and sunroom furniture.
    • Florian: Based in Georgetown, SC, Florian makes a variety of upper-end sunroom kits, along with greenhouses and conservatories. 
    • Colorado Sunroom and Window: Based in Denver, CO, Colorado Sunroom and Windows makes sunroom kits in a variety of styles, and quotes prices based on your specifications. 

    Final Word

    A sunroom is a fantastically tempting alternative to a conventional, full-sized addition. On average, these light-bathed spaces are cheaper than stick-built additions, and since fewer sub-contractors are involved, sunrooms go up quickly. Although the spaced added by a sunroom is defined as supplemental space—not the essential living space offered by room addition—for many homeowners, a sunroom is a perfect choice.