Wouldn't spray-foam insulation seal my house too tight?

Your house DOES need to be ventilated, BUT most home engineers & building scientists (as well as the US Dept of Energy) advise that you seal the structure as tight as possible & provide necessary ventilation through your air conditioning & heating system. Many systems employ an "air exchanger" which pre-conditions incoming outside air to control humidity & energy efficiency. This type of design along with spray-foam creates a true Thermal Envelope.