The cost of full room additions is similar to the cost of sunrooms, with parts and labor, plus a building permit and the frequency of use all factoring into the overall price. The increased materials used will also drive the cost up, and since room additions take more time to build than sunrooms, the labor hours will also increase the price.
Unlike sunrooms, which homeowners opt to use in part of the year, a full room addition needs insulation and to be fitted with electrical and best air conditioner connections to make it usable all year round. The use of full room addition may also help offset the overall price.
For example, if you use it only occasionally, maybe as a guest bedroom, the infrequent use may help you save money when it comes to household costs. But a frequently used entertainment or living room, complete with additional electronics, may increase your household costs.