Tewin Water House, Apartment 3, Tewin Water, Welwyn, AL6 0AA

Tewin Water House is a four-bedroom detached house in Welwyn (AL6 0AA). It has a recorded floor area of 360 m² (around 3878 sq ft), construction records dating it to before 1900 and council tax band G. It is a listed building, which means external alterations are tightly controlled but it may qualify for heritage tax reliefs. Other recorded features include attached land beyond the plot. Period features are noted in the property record. At 360 m² this is the 4th smallest of 5 units on EPC record in Tewin Water House, where floor areas span 154–588 m². The building's EPC ratings span E to C, with this unit at the bottom. On EPC score it ranks last in the building (54 versus a best of 71). The latest certificate (February 2012) shows an E (score 54), well below the UK norm with real room to improve. The recommended improvements would push it to D (score 56). The latest certificate is from February 2012, so improvements made since then won't be reflected.

It hasn't traded since November 2006, a hold of 20 years that's notably long for the area. At 360 m² the property is well over the postcode median (189 m² across 4 EPCs), placing it in the larger end of the local stock. On energy efficiency it sits in the bottom 10% of properties in this postcode — significant headroom for improvement. 4 bedrooms is on the larger side for this postcode, where 2 is the typical count. Across 2002–2006, sale prices on this property compounded at 8.8% per year. Today's modelled estimate of £1,659,000 sits 85.4% above the 2006 sale of £895,000. On a £-per-square-foot basis, the last sale (£231/sq ft) was about 20% below the postcode norm. 5 planning records sit against the property, 2 approved, 1 refused. Past consents include new windows, meaningful when judging how the property has evolved.