With the cost of housing still on an inexorable rise in the metro area, Englewood architect Randal Friesen sees accessory dwelling units as a key to solving the area’s affordable housing puzzle. The only problem is that new ADUs — think “granny flats” or “garden cottages” that are often used to house an aging parent or a child not quite ready to fly the nest — weren’t allowed in Englewood. Until now. On Monday, the city council narrowly approved an ordinance allowing ADUs to be established in more than half of Englewood’s residential zoned areas.