Does "open house" here refer to something about the structural design, or to the house being unlocked ? In English, an "open house" can be a party that people have when they move into a new house, or an event staged by a real estate salesperson in which a house that's for sale is open for potential buyers to stop in and tour.
Open huis has the same real estate event meaning in Dutch (open huizendag), but saying it is an open house to me sounds like the structural design, not the real estate event. Een open keuken is a common term, indicating the kitchen and living room are not separate rooms, also open could indicate a lot of windows and a connection to the surroundings.
For the open huizendag you can come across sentences like: ze houden open huis (they are having an open house) or het is open huis in dat huis (it is open house in that house) - sorry for the English sentences these are probably a bit odd.
In Dutch open huis normally is only used for houses that are publicly opened, for a (private) party after moving into a new house house warming party is used (yes we use the English term).
Thank you! The cultural context is additionally helpful - and interesting. I think in English we tend to use the term "open plan" for a house in which the kitchen, living, and dining area are more or less one room. I'm not sure we have a term for a house with a lot of windows, or one with a lot of connection to the outside.