Ibsen devotes nearly 300 words to describing the interior of the villa as the prelude to Act I. This demonstrates the importance of the theme of home in Hedda Gabler. Other relevant aspects are that, despite the showcase style of home, Hedda feels trapped and imprisoned; she feels alienated; she feels antagonistic toward those she shares home with; roles and responsibilities of home bring out her feelings of selfishness and acts of manipulation.
You need to remember that Hedda actually does not like her home whereas her husband talks about it as being their "dream home." Misconceptions and miscommunication are therefore very important when we think about this concept of "home." This is something that we see plays a vital part in their relationship, as we later discover that Hedda only married her husband because she thought he would be rich and famous.
My sense is that Hedda has no concept of what "home" really is. We get the sense that George and his aunt are family, as well as Berta. The relationship between these people has been established over time, based upon a mutual love for each other. No matter what building these people would live in, they would always be at home with each other because of their concern and admiration for each other.
Hedda obviously does not fit in. It is not because she has not been welcomed or because she is shy. Hedda shows no sign of wanting to be a part of the family: in fact, she seems to resent it and begins by trying to break things up making Aunt Julia feel unwelcome and insisting that Berta be fired. Hedda does not understand the compassion people feel for others, and this may well indicate that a family connection is something she neither understands or wants. She only wants things her way.
Hedda would never feel at home in George's house or with his family for she seems incapable of feeling love for others. George's home is a haven, a place of acceptance and support, and Hedda does not fit in there...by choice.
The concept of home is not a physical building, but an emotional place. As I noted, George, Julia and Berta would be at home in any building they lived in.
Litteacher nailed it on the head here. A home is a place where one is meant to feel comfortable, secure, and welcome. A home is not defined by where one lives, but what they fill that shelter with. For Hedda, her dwelling never was able to create a true home based upon the fact that she was unable to fill it with love, comfort, and security.
As a concept, home is a place you should feel comfortable and safe. It involves the presence of loved ones. When you marry, you create a new home. Because she does not love her new husband, she does not have a home.
How is the lighting in the house important? Because I found some places in the book where it describes the light coming into the house or any other light.