While 60 percent of homeowners consider their homes “healthy,” more than one in four are uncertain of major health hazards both indoors and out, according to the first “Healthy Home Trends” study of Houzz users in the United States.

The study also found that the majority of homes lack both health-promoting and safety systems, including things like carbon monoxide detectors. Homeowners recognize the need to address these gaps, and nearly half say preventing health problems and maintaining a healthy lifestyle are motivating factors for home renovation.

“Homeowners have a large gap between how healthy they perceive their homes to be and their awareness of real health hazards,” said Nino Sitchinava, principal economist at Houzz. “Houzz recognizes that health in the home is an important topic for our community. We will continue to empower people to make the best decisions for their home projects by providing actionable insights, guides and advice.”

Compared to homeowners who rated their homes “non-healthy,” homeowners with “healthy” houses tend to have newer homes, report better natural and artificial lighting, as well as lower levels of noise, allergens and mold and fewer encounters with pests than homeowners who rated their homes as “unhealthy.”

On average, however, over one in four of all homeowners say they are uncertain about many risk factors inside their home, including contaminants in drinking water, formaldehyde, lead and exhaust from gas-burning appliances or furnaces. A fifth (21 percent) of owners of “healthy” homes and over a third (34 percent) of owners of “non-healthy” homes said they weren’t sure about the presence of asbestos in their homes.

The prevalence of health-promoting systems is low in all homes, irrespective of health perceptions. Whole house ventilation systems and even inexpensive stand-alone fans are absent from over half of “healthy” homes and over two-thirds of “non-healthy” homes. Only half of homes have (de)humidification systems or devices, and less than a third have air purification systems or devices. Nearly a third of all homes lack windows or skylights in each room.

Despite the low prevalence of health-promoting systems in all houses, homeowners who rated their homes as healthy were more likely to have made upgrades in the past 12 months, with interior painting (41 percent), lighting (28 percent), flooring (27 percent), windows (21 percent) and insulation (20 percent) topping the list of improvements.

One in five owners of “healthy” homes also upgraded their HVAC system in the past 12 months. Those who rated their homes as less healthy are more likely to renovate these systems in the next 12 months.

This study surveyed 808 U.S. homeowners using Houzz in October 2014. The full Houzz Healthy Home Trends Study can be downloaded here.