Dunelm Group, a homewares retailer, said its revenues increased during the first half of the financial year despite a rise in operating costs.The retailer sold £406.4m during the first half in December, compared to £356.4m the year before.The furniture department sold £20m, an increase of 60%, while its online business expanded with deliveries increasing by 70%.Operating expenditure rose due to investment in new stores, staff and marketing, online home delivery fulfilment and development in support functions like IT and merchandising.The group expects to open six new stores by the end of the financial year. In total, Dunelm will be operating 148 superstores in the UK.Chief executive Will Adderley said: "Whilst we were up against weak comparatives in the first quarter, this was not the case in the second quarter so like for like growth of over 4% in that period is a strong result."My priority going forward is to achieve growth consistently from each of our channels, including our core superstore format. We are excited by the opportunities available to us both from stores and online and we will continue to make the capital and revenue investments necessary to seize them."Shares were up 3.16% to 882p on Thursday at 9:51.