When converting to group housing for sows if remodeling of the previous ventilation systems does not occur, it is estimated that over-ventilating will occur at a rate of 30%. This will raise the heating energy consumption by 75% in the winter. Carefully redesigning the ventilation system will aid in ensuring optimal pig health as well as reducing energy costs. Through the use of computer stimulation it was determined that utilizing a horizontal flow ventilation system (having the air inlets located opposite to the exhaust fans) resulted in the air being most effectively homogeneously mixed. Utilizing the horizontal flow ventilation system (HFVS) an in-barn evaluation was carried out to determine the ventilation effectiveness on temperature and HRE (heat removal effectiveness), air quality, sow condition and performance, and the behavior of the sow. When comparing the remodeled ventilation system to the unmodified system it is apparent that the modified system more effective at removing heat and contaminants (such as CO2) from the room. In the room equipped with the HFVS the sows displayed a higher level of comfort and were overall less aggressive towards other sows. The in barn evaluation determined that when comparing a converted room with an unmodified ventilation system to group housing with a HFVS that the HFVS resulted in a 21% reduction in natural gas consumption and a 14% reduction in electricity consumption.