def uVal(thick):
    """Compute the wals U-value starting from the thickness of 
    the insulation layer
    
    Parameters
    ----------
    thick : float
        insulation thickness in m
    """
    R_th = .17
    layers = [
		{
			'Thickness':.025,
			'Conductivity':.33
		},{
			'Thickness':thick,
			'Conductivity':.047
		},{
			'Thickness':.2,
			'Conductivity':.51
		},{
			'Thickness':.013,
			'Conductivity':.4
		},
	]
	
    res = R_th
    for item in layers:
        res+=item['Thickness']/item['Conductivity']
	
    return 1/res