I am an engineer and former project manager for a Green Building General Contractor.
This is the first post I have read where some important answers are completely wrong. I wish people who have no idea what they are talking about (Vicki and Lynn) would just keep quiet.
Modular homes, which are frequently confused with manufactured (formerly called mobile) homes, are designed, permitted and constructed to meet all applicable building codes exactly like a site built structure.
After the plans are approved by the local building authority, modular homes are built in sections in a factory setting, indoors, where they are never subjected to adverse weather conditions. The sections move through the factory, with the company's quality control department checking them after every step. Finished modules are covered for protection, then transported to the home site. They are placed on a slab or crawl space foundation just like a site built house, joined, and completed by the contractor and inspected by the local building authority throughout the process.
A modular home is far better constructed and subjected to much more quality control measures than any site built home. Modular homes are also far better insulated and can be easily designed to achieve an Energy Star rating wheras almost no site built home can achieve this rating. To earn the ENERGY STAR, a home must meet strict guidelines for energy efficiency set by the U.S. Environmental Protection Agency. These homes are at least 15% more energy efficient than homes built to the 2004 International Residential Code (IRC), and include additional energy-saving features that typically make them 20â€“30% more efficient than standard homes.
On the other hand:
WHAT ARE MANUFACTURED HOMES?
Manufactured homes means a structure subject to federal regulation, which is
transportable in one or more sections; is eight body feet or more in width and
forty body feet or more in length in the traveling mode, or is 320 or more square
feet when erected on site; is built on a permanent chassis; is designed to be used
as a single-family dwelling, with or without a permanent foundation, when
connected to the required utilities; and includes the plumbing, heating, airconditioning,
and electrical system contained in the structure.
MANUFACTURED HOME ADMINISTRATION AND ENFORCEMENT â€“ HUD
Manufactured homes are designed, constructed, and approved under a Federal
program administered by the U. S. Department of Housing and Urban
Development (HUD). HUD promulgates standards, which may not be
superseded or amended by state or local governments. State or private agencies
are accredited and monitored by HUD to review designs and inspect
construction of homes to assure compliance with Federal construction standards.
State or local code officials may not enforce construction requirements, which
conflict with any HUD standards for manufactured homes.